Text: introduce Alignment::*Start and *End.

Based on the actual text direction (either explicitly set or detected),
these resolve to either *Left or *Right. For the Text::Renderer it's
done automatically inside (and there's no way to actually set the
direction from outside due to the API being ancient and limited), for
the align*() utils the alignment has to be explicitly resolved using a
new alignmentForDirection() utility.

doc/changelog.dox

@@ -834,6 +834,11 @@ See also:
     missing before, and @ref Text::Alignment::TopCenterIntegral, which is also
     needed in order to prevent aligning pixel-perfect fonts to fractional
     positions.
+-   @ref Text::Alignment gained special `*Start` and `*End` values for
+    alignment based on text direction, and a new
+    @ref Text::alignmentForDirection() utility that resolves those to concrete
+    `*Left` and `*Right` values based @ref Text::LayoutDirection and
+    @ref Text::ShapeDirection
 -   Added a @ref Text::GlyphCache::GlyphCache(NoCreateT) and
     @ref Text::DistanceFieldGlyphCache::DistanceFieldGlyphCache(NoCreateT)
     constructor allowing to construct the object without a GL context present

src/Magnum/Text/Alignment.cpp

@@ -25,8 +25,11 @@
 
 #include "Alignment.h"
 
+#include <Corrade/Utility/Assert.h>
 #include <Corrade/Utility/Debug.h>
 
+#include "Magnum/Text/Direction.h"
+
 namespace Magnum { namespace Text {
 
 Debug& operator<<(Debug& debug, const Alignment value) {
@@ -43,6 +46,10 @@ Debug& operator<<(Debug& debug, const Alignment value) {
         _c(LineCenterGlyphBoundsIntegral)
         _c(LineRight)
         _c(LineRightGlyphBounds)
+        _c(LineStart)
+        _c(LineStartGlyphBounds)
+        _c(LineEnd)
+        _c(LineEndGlyphBounds)
         _c(BottomLeft)
         _c(BottomLeftGlyphBounds)
         _c(BottomCenter)
@@ -51,6 +58,10 @@ Debug& operator<<(Debug& debug, const Alignment value) {
         _c(BottomCenterGlyphBoundsIntegral)
         _c(BottomRight)
         _c(BottomRightGlyphBounds)
+        _c(BottomStart)
+        _c(BottomStartGlyphBounds)
+        _c(BottomEnd)
+        _c(BottomEndGlyphBounds)
         _c(MiddleLeft)
         _c(MiddleLeftIntegral)
         _c(MiddleLeftGlyphBounds)
@@ -63,6 +74,14 @@ Debug& operator<<(Debug& debug, const Alignment value) {
         _c(MiddleRightIntegral)
         _c(MiddleRightGlyphBounds)
         _c(MiddleRightGlyphBoundsIntegral)
+        _c(MiddleStart)
+        _c(MiddleStartIntegral)
+        _c(MiddleStartGlyphBounds)
+        _c(MiddleStartGlyphBoundsIntegral)
+        _c(MiddleEnd)
+        _c(MiddleEndIntegral)
+        _c(MiddleEndGlyphBounds)
+        _c(MiddleEndGlyphBoundsIntegral)
         _c(TopLeft)
         _c(TopLeftGlyphBounds)
         _c(TopCenter)
@@ -71,6 +90,10 @@ Debug& operator<<(Debug& debug, const Alignment value) {
         _c(TopCenterGlyphBoundsIntegral)
         _c(TopRight)
         _c(TopRightGlyphBounds)
+        _c(TopStart)
+        _c(TopStartGlyphBounds)
+        _c(TopEnd)
+        _c(TopEndGlyphBounds)
         #undef _c
         /* LCOV_EXCL_STOP */
     }
@@ -78,4 +101,25 @@ Debug& operator<<(Debug& debug, const Alignment value) {
     return debug << "(" << Debug::nospace << Debug::hex << UnsignedByte(value) << Debug::nospace << ")";
 }
 
+Alignment alignmentForDirection(const Alignment alignment, const LayoutDirection layoutDirection, const ShapeDirection shapeDirection) {
+    CORRADE_ASSERT(layoutDirection == LayoutDirection::HorizontalTopToBottom,
+        "Text::alignmentForDirection(): only" << LayoutDirection::HorizontalTopToBottom << "is supported right now, got" << layoutDirection, {});
+    CORRADE_ASSERT(shapeDirection != ShapeDirection::TopToBottom &&
+                   shapeDirection != ShapeDirection::BottomToTop,
+        "Text::alignmentForDirection():" << shapeDirection << "is not supported yet, sorry", {});
+
+    const UnsignedByte horizontal = UnsignedByte(alignment) & Implementation::AlignmentHorizontal;
+    const UnsignedByte exceptHorizontal = UnsignedByte(alignment) & ~Implementation::AlignmentHorizontal;
+    if(horizontal == Implementation::AlignmentStart)
+        return Alignment((shapeDirection == ShapeDirection::RightToLeft ?
+            Implementation::AlignmentRight :
+            Implementation::AlignmentLeft)|exceptHorizontal);
+    if(horizontal == Implementation::AlignmentEnd)
+        return Alignment((shapeDirection == ShapeDirection::RightToLeft ?
+            Implementation::AlignmentLeft :
+            Implementation::AlignmentRight)|exceptHorizontal);
+
+    return alignment;
+}
+
 }}

src/Magnum/Text/Alignment.h

@@ -26,10 +26,11 @@
 */
 
 /** @file
- * @brief Enum @ref Magnum::Text::Alignment
+ * @brief Enum @ref Magnum::Text::Alignment, function @ref Magnum::Text::alignmentForDirection()
  */
 
 #include "Magnum/Magnum.h"
+#include "Magnum/Text/Text.h"
 #include "Magnum/Text/visibility.h"
 
 namespace Magnum { namespace Text {
@@ -42,16 +43,20 @@ namespace Implementation {
         AlignmentLeft = 0,
         AlignmentCenter = 1 << 0,
         AlignmentRight = 2 << 0,
-        AlignmentHorizontal = AlignmentLeft|AlignmentCenter|AlignmentRight,
+        /* Start and End is Left or Right based on ShapeDirection, and possibly
+           also Top / Bottom eventually for vertical text */
+        AlignmentStart = 3 << 0,
+        AlignmentEnd = 4 << 0,
+        AlignmentHorizontal = AlignmentLeft|AlignmentCenter|AlignmentRight|AlignmentStart|AlignmentEnd,
 
         AlignmentLine = 0,
-        AlignmentBottom = 1 << 2,
-        AlignmentMiddle = 2 << 2,
-        AlignmentTop = 3 << 2,
+        AlignmentBottom = 1 << 4,
+        AlignmentMiddle = 2 << 4,
+        AlignmentTop = 3 << 4,
         AlignmentVertical = AlignmentLine|AlignmentBottom|AlignmentMiddle|AlignmentTop,
 
-        AlignmentIntegral = 1 << 4,
-        AlignmentGlyphBounds = 1 << 5
+        AlignmentIntegral = 1 << 6,
+        AlignmentGlyphBounds = 1 << 7
     };
 }
 
@@ -71,19 +76,31 @@ positioned on whole pixels as well in order to avoid making them blurry. These
 are only needed for `*Middle` and `*Center` alignments as they may result in
 the bounding rectangle to have odd dimensions, which would then result in
 half-pixel shifts when divided by 2.
-@see @ref Renderer::render(), @ref Renderer::Renderer()
+
+The `*Start` and `*End` values behave the same as `*Left` and `*Right`,
+respectively, if @ref ShapeDirection::LeftToRight is passed to
+@ref AbstractShaper::setDirection(), or if it's
+@ref ShapeDirection::Unspecified and the particular font plugin doesn't detect
+@ref ShapeDirection::RightToLeft when shaping. If
+@ref ShapeDirection::RightToLeft is set (or detected for
+@ref ShapeDirection::Unspecified), they're swapped, i.e. `*Start` becomes
+`*Right` and `*End` becomes `*Left`.
+@see @ref Renderer::render(), @ref Renderer::Renderer(),
+    @see @ref alignmentForDirection()
 */
 enum class Alignment: UnsignedByte {
     /**
      * Leftmost cursor position and vertical line position is at origin.
-     * @see @ref Alignment::LineLeftGlyphBounds
+     * @see @ref Alignment::LineLeftGlyphBounds, @ref Alignment::LineStart,
+     *      @ref Alignment::LineEnd
      */
     LineLeft = Implementation::AlignmentLine|Implementation::AlignmentLeft,
 
     /**
      * Left side of the glyph bounding rectangle and vertical line position is
      * at origin.
-     * @see @ref Alignment::LineLeft
+     * @see @ref Alignment::LineLeft, @ref Alignment::LineStartGlyphBounds,
+     *      @ref Alignment::LineEndGlyphBounds
      * @m_since_latest
      */
     LineLeftGlyphBounds = LineLeft|Implementation::AlignmentGlyphBounds,
@@ -126,28 +143,68 @@ enum class Alignment: UnsignedByte {
 
     /**
      * Rightmost cursor position and vertical line position is at origin.
-     * @see @ref Alignment::LineRightGlyphBounds
+     * @see @ref Alignment::LineRightGlyphBounds, @ref Alignment::LineEnd,
+     *      @ref Alignment::LineStart
+     * @see @ref alignmentForDirection()
      */
     LineRight = Implementation::AlignmentLine|Implementation::AlignmentRight,
 
     /**
      * Right side of the glyph bounding rectangle and vertical line position is
      * at origin.
-     * @see @ref Alignment::LineRight
+     * @see @ref Alignment::LineRight, @ref Alignment::LineEndGlyphBounds,
+     *      @ref Alignment::LineStartGlyphBounds
+     * @see @ref alignmentForDirection()
      * @m_since_latest
      */
     LineRightGlyphBounds = LineRight|Implementation::AlignmentGlyphBounds,
 
+    /**
+     * @ref Alignment::LineRight for @ref ShapeDirection::RightToLeft,
+     * @ref Alignment::LineLeft otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    LineStart = Implementation::AlignmentLine|Implementation::AlignmentStart,
+
+    /**
+     * @ref Alignment::LineRightGlyphBounds for
+     * @ref ShapeDirection::RightToLeft, @ref Alignment::LineLeftGlyphBounds
+     * otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    LineStartGlyphBounds = LineStart|Implementation::AlignmentGlyphBounds,
+
+    /**
+     * @ref Alignment::LineLeft for @ref ShapeDirection::RightToLeft,
+     * @ref Alignment::LineRight otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    LineEnd = Implementation::AlignmentLine|Implementation::AlignmentEnd,
+
+    /**
+     * @ref Alignment::LineLeftGlyphBounds for
+     * @ref ShapeDirection::RightToLeft, @ref Alignment::LineRightGlyphBounds
+     * otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    LineEndGlyphBounds = LineEnd|Implementation::AlignmentGlyphBounds,
+
     /**
      * Leftmost cursor position and bottommost line descent is at origin.
-     * @see @ref Alignment::BottomLeftGlyphBounds
+     * @see @ref Alignment::BottomLeftGlyphBounds, @ref Alignment::BottomStart,
+     *      @ref Alignment::BottomEnd
      * @m_since_latest
      */
     BottomLeft = Implementation::AlignmentBottom|Implementation::AlignmentLeft,
 
     /**
      * Bottom left corner of the glyph bounding rectangle is at origin.
-     * @see @ref Alignment::BottomLeft
+     * @see @ref Alignment::BottomLeft, @ref Alignment::BottomStartGlyphBounds,
+     *      @ref Alignment::BottomEndGlyphBounds
      * @m_since_latest
      */
     BottomLeftGlyphBounds = BottomLeft|Implementation::AlignmentGlyphBounds,
@@ -191,23 +248,60 @@ enum class Alignment: UnsignedByte {
 
     /**
      * Rightmost cursor position and bottommost line descent is at origin.
-     * @see @ref Alignment::BottomRightGlyphBounds
+     * @see @ref Alignment::BottomRightGlyphBounds, @ref Alignment::BottomEnd,
+     *      @ref Alignment::BottomStart
      * @m_since_latest
      */
     BottomRight = Implementation::AlignmentBottom|Implementation::AlignmentRight,
 
     /**
      * Bottom right corner of the glyph bounding rectangle is at origin.
-     * @see @ref Alignment::BottomRight
+     * @see @ref Alignment::BottomRight, @ref Alignment::BottomEndGlyphBounds,
+     *      @ref Alignment::BottomStartGlyphBounds
      * @m_since_latest
      */
     BottomRightGlyphBounds = BottomRight|Implementation::AlignmentGlyphBounds,
 
+    /**
+     * @ref Alignment::BottomRight for @ref ShapeDirection::RightToLeft,
+     * @ref Alignment::BottomLeft otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    BottomStart = Implementation::AlignmentBottom|Implementation::AlignmentStart,
+
+    /**
+     * @ref Alignment::BottomRightGlyphBounds for
+     * @ref ShapeDirection::RightToLeft, @ref Alignment::BottomLeftGlyphBounds
+     * otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    BottomStartGlyphBounds = BottomStart|Implementation::AlignmentGlyphBounds,
+
+    /**
+     * @ref Alignment::BottomLeft for @ref ShapeDirection::RightToLeft,
+     * @ref Alignment::BottomRight otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    BottomEnd = Implementation::AlignmentBottom|Implementation::AlignmentEnd,
+
+    /**
+     * @ref Alignment::BottomLeftGlyphBounds for
+     * @ref ShapeDirection::RightToLeft, @ref Alignment::BottomRightGlyphBounds
+     * otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    BottomEndGlyphBounds = BottomEnd|Implementation::AlignmentGlyphBounds,
+
     /**
      * Leftmost cursor position and a midpoint between topmost line ascent and
      * bottommost line descent is at origin.
      * @see @ref Alignment::MiddleLeftGlyphBounds,
-     *      @ref Alignment::MiddleLeftIntegral
+     *      @ref Alignment::MiddleLeftIntegral, @ref Alignment::MiddleStart,
+     *      @ref Alignment::MiddleEnd
      */
     MiddleLeft = Implementation::AlignmentMiddle|Implementation::AlignmentLeft,
 
@@ -216,7 +310,9 @@ enum class Alignment: UnsignedByte {
      * bottommost line descent is at origin, with the vertical offset rounded
      * to whole units.
      * @see @ref Alignment::MiddleLeft,
-     *      @ref Alignment::MiddleLeftGlyphBoundsIntegral
+     *      @ref Alignment::MiddleLeftGlyphBoundsIntegral,
+     *      @ref Alignment::MiddleStartIntegral,
+     *      @ref Alignment::MiddleEndIntegral
      */
     MiddleLeftIntegral = MiddleLeft|Implementation::AlignmentIntegral,
 
@@ -224,7 +320,9 @@ enum class Alignment: UnsignedByte {
      * Left side and vertical center of the glyph bounding rectangle is at
      * origin.
      * @see @ref Alignment::MiddleLeft,
-     *      @ref Alignment::MiddleLeftGlyphBoundsIntegral
+     *      @ref Alignment::MiddleLeftGlyphBoundsIntegral,
+     *      @ref Alignment::MiddleStartGlyphBounds,
+     *      @ref Alignment::MiddleEndGlyphBounds
      * @m_since_latest
      */
     MiddleLeftGlyphBounds = MiddleLeft|Implementation::AlignmentGlyphBounds,
@@ -233,7 +331,9 @@ enum class Alignment: UnsignedByte {
      * Left side and vertical center of the glyph bounding rectangle is at
      * origin, with the vertical offset rounded to whole units.
      * @see @ref Alignment::MiddleLeftGlyphBounds,
-     *      @ref Alignment::MiddleLeftIntegral
+     *      @ref Alignment::MiddleLeftIntegral,
+     *      @ref Alignment::MiddleStartGlyphBoundsIntegral,
+     *      @ref Alignment::MiddleEndGlyphBoundsIntegral
      * @m_since_latest
      */
     MiddleLeftGlyphBoundsIntegral = MiddleLeftGlyphBounds|Implementation::AlignmentIntegral,
@@ -278,7 +378,8 @@ enum class Alignment: UnsignedByte {
      * Rightmost cursor position and a midpoint between topmost line ascent and
      * bottommost line descent is at origin.
      * @see @ref Alignment::MiddleRightGlyphBounds,
-     *      @ref Alignment::MiddleRightIntegral
+     *      @ref Alignment::MiddleRightIntegral, @ref Alignment::MiddleEnd,
+     *      @ref Alignment::MiddleStart
      */
     MiddleRight = Implementation::AlignmentMiddle|Implementation::AlignmentRight,
 
@@ -287,7 +388,9 @@ enum class Alignment: UnsignedByte {
      * bottommost line descent is at origin, with the vertical offset rounded
      * to whole units.
      * @see @ref Alignment::MiddleRight,
-     *      @ref Alignment::MiddleRightGlyphBoundsIntegral
+     *      @ref Alignment::MiddleRightGlyphBoundsIntegral,
+     *      @ref Alignment::MiddleEndIntegral,
+     *      @ref Alignment::MiddleStartIntegral
      */
     MiddleRightIntegral = MiddleRight|Implementation::AlignmentIntegral,
 
@@ -295,7 +398,9 @@ enum class Alignment: UnsignedByte {
      * Right side and vertical center of the glyph bounding rectangle is at
      * origin.
      * @see @ref Alignment::MiddleRight,
-     *      @ref Alignment::MiddleRightGlyphBoundsIntegral
+     *      @ref Alignment::MiddleRightGlyphBoundsIntegral,
+     *      @ref Alignment::MiddleEndGlyphBounds,
+     *      @ref Alignment::MiddleStartGlyphBounds
      * @m_since_latest
      */
     MiddleRightGlyphBounds = MiddleRight|Implementation::AlignmentGlyphBounds,
@@ -304,20 +409,94 @@ enum class Alignment: UnsignedByte {
      * Right side and vertical center of the glyph bounding rectangle is at
      * origin, with the vertical offset rounded to whole units.
      * @see @ref Alignment::MiddleRightGlyphBounds,
-     *      @ref Alignment::MiddleRightIntegral
+     *      @ref Alignment::MiddleRightIntegral,
+     *      @ref Alignment::MiddleEndGlyphBoundsIntegral,
+     *      @ref Alignment::MiddleStartGlyphBoundsIntegral
      * @m_since_latest
      */
     MiddleRightGlyphBoundsIntegral = MiddleRightGlyphBounds|Implementation::AlignmentIntegral,
 
+    /**
+     * @ref Alignment::MiddleRight for @ref ShapeDirection::RightToLeft,
+     * @ref Alignment::MiddleLeft otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    MiddleStart = Implementation::AlignmentMiddle|Implementation::AlignmentStart,
+
+    /**
+     * @ref Alignment::MiddleRightIntegral for
+     * @ref ShapeDirection::RightToLeft, @ref Alignment::MiddleLeftIntegral
+     * otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    MiddleStartIntegral = MiddleStart|Implementation::AlignmentIntegral,
+
+    /**
+     * @ref Alignment::MiddleRightGlyphBounds for
+     * @ref ShapeDirection::RightToLeft, @ref Alignment::MiddleLeftGlyphBounds
+     * otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    MiddleStartGlyphBounds = MiddleStart|Implementation::AlignmentGlyphBounds,
+
+    /**
+     * @ref Alignment::MiddleRightGlyphBoundsIntegral for
+     * @ref ShapeDirection::RightToLeft,
+     * @ref Alignment::MiddleLeftGlyphBoundsIntegral otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    MiddleStartGlyphBoundsIntegral = MiddleStartGlyphBounds|Implementation::AlignmentIntegral,
+
+    /**
+     * @ref Alignment::MiddleLeft for @ref ShapeDirection::RightToLeft,
+     * @ref Alignment::MiddleRight otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    MiddleEnd = Implementation::AlignmentMiddle|Implementation::AlignmentEnd,
+
+    /**
+     * @ref Alignment::MiddleLeftIntegral for
+     * @ref ShapeDirection::RightToLeft, @ref Alignment::MiddleRightIntegral
+     * otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    MiddleEndIntegral = MiddleEnd|Implementation::AlignmentIntegral,
+
+    /**
+     * @ref Alignment::MiddleLeftGlyphBounds for
+     * @ref ShapeDirection::RightToLeft, @ref Alignment::MiddleRightGlyphBounds
+     * otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    MiddleEndGlyphBounds = MiddleEnd|Implementation::AlignmentGlyphBounds,
+
+    /**
+     * @ref Alignment::MiddleLeftGlyphBoundsIntegral for
+     * @ref ShapeDirection::RightToLeft,
+     * @ref Alignment::MiddleRightGlyphBoundsIntegral otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    MiddleEndGlyphBoundsIntegral = MiddleEndGlyphBounds|Implementation::AlignmentIntegral,
+
     /**
      * Leftmost cursor position and topmost line ascent is at origin.
-     * @see @ref Alignment::TopLeftGlyphBounds
+     * @see @ref Alignment::TopLeftGlyphBounds, @ref Alignment::TopStart,
+     *      @ref Alignment::TopEnd
      */
     TopLeft = Implementation::AlignmentTop|Implementation::AlignmentLeft,
 
     /**
      * Top left corner of the glyph bounding rectangle is at origin.
-     * @see @ref Alignment::TopLeft
+     * @see @ref Alignment::TopLeft, @ref Alignment::TopStartGlyphBounds,
+     *      @ref Alignment::TopEndGlyphBounds
      * @m_since_latest
      */
     TopLeftGlyphBounds = TopLeft|Implementation::AlignmentGlyphBounds,
@@ -359,21 +538,72 @@ enum class Alignment: UnsignedByte {
 
     /**
      * Rightmost cursor position and topmost line ascent is at origin.
-     * @see @ref Alignment::TopRightGlyphBounds
+     * @see @ref Alignment::TopRightGlyphBounds, @ref Alignment::TopEnd,
+     *      @ref Alignment::TopStart
      */
     TopRight = Implementation::AlignmentTop|Implementation::AlignmentRight,
 
     /**
      * Top right corner of the glyph bounding rectangle is at origin.
-     * @see @ref Alignment::TopRight
+     * @see @ref Alignment::TopRight, @ref Alignment::TopEndGlyphBounds,
+     *      @ref Alignment::TopStartGlyphBounds
      * @m_since_latest
      */
     TopRightGlyphBounds = TopRight|Implementation::AlignmentGlyphBounds,
+
+    /**
+     * @ref Alignment::TopRight for @ref ShapeDirection::RightToLeft,
+     * @ref Alignment::TopLeft otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    TopStart = Implementation::AlignmentTop|Implementation::AlignmentStart,
+
+    /**
+     * @ref Alignment::TopRightGlyphBounds for
+     * @ref ShapeDirection::RightToLeft, @ref Alignment::TopLeftGlyphBounds
+     * otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    TopStartGlyphBounds = TopStart|Implementation::AlignmentGlyphBounds,
+
+    /**
+     * @ref Alignment::TopLeft for @ref ShapeDirection::RightToLeft,
+     * @ref Alignment::TopRight otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    TopEnd = Implementation::AlignmentTop|Implementation::AlignmentEnd,
+
+    /**
+     * @ref Alignment::TopLeftGlyphBounds for
+     * @ref ShapeDirection::RightToLeft, @ref Alignment::TopRightGlyphBounds
+     * otherwise.
+     * @see @ref alignmentForDirection()
+     * @m_since_latest
+     */
+    TopEndGlyphBounds = TopEnd|Implementation::AlignmentGlyphBounds,
 };
 
 /** @debugoperatorenum{Alignment} */
 MAGNUM_TEXT_EXPORT Debug& operator<<(Debug& debug, Alignment value);
 
+/**
+@brief Alignment for layout and shape direction
+@m_since_latest
+
+The @p layoutDirection is currently expected to always be
+@ref LayoutDirection::HorizontalTopToBottom and @p shapeDirection never
+@ref ShapeDirection::TopToBottom or @ref ShapeDirection::BottomToTop. Then, if
+@p alignment is `*Start` or `*End`, it's converted to `*Left` or `*Right`,
+respectively, if @p shapeDirection is @ref ShapeDirection::LeftToRight or
+@ref ShapeDirection::Unspecified, and `*Right` or `*Left`, respectively, if
+@p shapeDirection is @ref ShapeDirection::RightToLeft.
+*/
+MAGNUM_TEXT_EXPORT Alignment alignmentForDirection(Alignment alignment, LayoutDirection layoutDirection, ShapeDirection shapeDirection);
+
+
 }}
 
 #endif

src/Magnum/Text/CMakeLists.txt

@@ -31,7 +31,6 @@ find_package(Corrade REQUIRED PluginManager)
 
 # Files shared between main library and unit test library
 set(MagnumText_SRCS
-    Alignment.cpp
     Direction.cpp)
 
 # Files compiled with different flags for main library and unit test library
@@ -40,6 +39,7 @@ set(MagnumText_GracefulAssert_SRCS
     AbstractFontConverter.cpp
     AbstractGlyphCache.cpp
     AbstractShaper.cpp
+    Alignment.cpp
     Feature.cpp
     Renderer.cpp
     Script.cpp)

src/Magnum/Text/Renderer.cpp

@@ -188,6 +188,10 @@ Range2D renderGlyphQuadsInto(const AbstractGlyphCache& cache, const Float scale,
 Range2D alignRenderedLine(const Range2D& lineRectangle, const LayoutDirection direction, const Alignment alignment, const Containers::StridedArrayView1D<Vector2>& positions) {
     CORRADE_ASSERT(direction == LayoutDirection::HorizontalTopToBottom,
         "Text::alignRenderedLine(): only" << LayoutDirection::HorizontalTopToBottom << "is supported right now, got" << direction, {});
+    CORRADE_ASSERT(
+        (UnsignedByte(alignment) & Implementation::AlignmentHorizontal) != Implementation::AlignmentStart &&
+        (UnsignedByte(alignment) & Implementation::AlignmentHorizontal) != Implementation::AlignmentEnd,
+        "Text::alignRenderedLine():" << alignment << "has to be resolved to *Left / *Right before being passed to this function", {});
     #ifdef CORRADE_NO_ASSERT
     static_cast<void>(direction); /** @todo drop once implemented */
     #endif
@@ -218,6 +222,10 @@ Range2D alignRenderedLine(const Range2D& lineRectangle, const LayoutDirection di
 Range2D alignRenderedBlock(const Range2D& blockRectangle, const LayoutDirection direction, const Alignment alignment, const Containers::StridedArrayView1D<Vector2>& positions) {
     CORRADE_ASSERT(direction == LayoutDirection::HorizontalTopToBottom,
         "Text::alignRenderedBlock(): only" << LayoutDirection::HorizontalTopToBottom << "is supported right now, got" << direction, {});
+    CORRADE_ASSERT(
+        (UnsignedByte(alignment) & Implementation::AlignmentHorizontal) != Implementation::AlignmentStart &&
+        (UnsignedByte(alignment) & Implementation::AlignmentHorizontal) != Implementation::AlignmentEnd,
+        "Text::alignRenderedBlock():" << alignment << "has to be resolved to *Left / *Right before being passed to this function", {});
     #ifdef CORRADE_NO_ASSERT
     static_cast<void>(direction); /** @todo drop once implemented */
     #endif
@@ -335,6 +343,12 @@ std::tuple<std::vector<Vertex>, Range2D> renderVerticesInternal(AbstractFont& fo
     /** @todo even with reusing a shaper this is all horrific, rework!! */
     Containers::Pointer<AbstractShaper> shaper = font.createShaper();
 
+    /* Start/End alignment resolved based on what the shaper detects for the
+       first line. Not great, but can't do much better with this old limited
+       API. */
+    /** @todo rework all this, again */
+    Containers::Optional<Alignment> resolvedAlignment;
+
     /* Render each line separately and align it horizontally */
     std::size_t pos, prevPos = 0;
     do {
@@ -404,14 +418,30 @@ std::tuple<std::vector<Vertex>, Range2D> renderVerticesInternal(AbstractFont& fo
             lineVertices.slice(&Vertex::position),
             lineVertices.slice(&Vertex::textureCoordinates));
 
+        /* Resolve the alignment based on what the shaper detected (if
+           anything). Assume there are no font plugins that would produce
+           vertical shape direction by default. */
+        /** @todo drop all this once the shaper instance is configurable from
+            outside */
+        if(!resolvedAlignment) {
+            const ShapeDirection shapeDirection = shaper->direction();
+            CORRADE_INTERNAL_ASSERT(
+                shapeDirection != ShapeDirection::TopToBottom &&
+                shapeDirection != ShapeDirection::BottomToTop);
+            resolvedAlignment = alignmentForDirection(alignment,
+                /** @todo direction hardcoded here */
+                LayoutDirection::HorizontalTopToBottom,
+                shapeDirection);
+        }
+
         /* Horizontally align the line, using either of the rectangles based on
            which alignment is desired */
         const Range2D alignedLineRectangle = alignRenderedLine(
-            UnsignedByte(alignment) & Implementation::AlignmentGlyphBounds ?
+            UnsignedByte(*resolvedAlignment) & Implementation::AlignmentGlyphBounds ?
                 lineQuadRectangle : lineRectangle,
             /** @todo direction hardcoded here */
             LayoutDirection::HorizontalTopToBottom,
-            alignment,
+            *resolvedAlignment,
             lineVertices.slice(&Vertex::position));
 
         /* Extend the rectangle with final line bounds */
@@ -426,7 +456,7 @@ std::tuple<std::vector<Vertex>, Range2D> renderVerticesInternal(AbstractFont& fo
         rectangle,
         /** @todo direction hardcoded here */
         LayoutDirection::HorizontalTopToBottom,
-        alignment,
+        *resolvedAlignment,
         Containers::stridedArrayView(vertices).slice(&Vertex::position));
 
     return std::make_tuple(Utility::move(vertices), alignedRectangle);

src/Magnum/Text/Renderer.h

@@ -212,6 +212,11 @@ MAGNUM_TEXT_EXPORT Range2D renderGlyphQuadsInto(const AbstractGlyphCache& cache,
     the alignment.
 @m_since_latest
 
+Expects that @p alignment isn't `*Start` or `*End`, those values have to be
+resolved to `*Left` or `*Right` based on desired or detected
+@ref ShapeDirection using @ref alignmentForDirection() before being passed to
+this function.
+
 If @p alignment isn't `*GlyphBounds`, this function should get glyph
 @p positions for the whole line coming from @ref renderLineGlyphPositionsInto()
 and @p lineRectangle being all rectangles returned by that function combined
@@ -244,6 +249,11 @@ MAGNUM_TEXT_EXPORT Range2D alignRenderedLine(const Range2D& lineRectangle, Layou
     advance based on the alignment.
 @m_since_latest
 
+Expects that @p alignment isn't `*Start` or `*End`, those values have to be
+resolved to `*Left` or `*Right` based on desired or detected
+@ref ShapeDirection using @ref alignmentForDirection() before being passed to
+this function.
+
 This function should get glyph or vertex @p positions for all lines as aligned
 by calls to @ref alignRenderedLine(), and @p blockRectangle being all line
 rectangles returned by that function combined together with @ref Math::join().

src/Magnum/Text/Test/AlignmentTest.cpp

@@ -24,10 +24,13 @@
 */
 
 #include <sstream>
+#include <Corrade/Containers/StringStl.h> /** @todo remove once Debug is stream-free */
 #include <Corrade/TestSuite/Tester.h>
+#include <Corrade/TestSuite/Compare/String.h>
 #include <Corrade/Utility/DebugStl.h> /** @todo remove once Debug is stream-free */
 
 #include "Magnum/Text/Alignment.h"
+#include "Magnum/Text/Direction.h"
 
 namespace Magnum { namespace Text { namespace Test { namespace {
 
@@ -35,10 +38,16 @@ struct AlignmentTest: TestSuite::Tester {
     explicit AlignmentTest();
 
     void debug();
+
+    void forDirection();
+    void forDirectionInvalid();
 };
 
 AlignmentTest::AlignmentTest() {
-    addTests({&AlignmentTest::debug});
+    addTests({&AlignmentTest::debug,
+
+              &AlignmentTest::forDirection,
+              &AlignmentTest::forDirectionInvalid});
 }
 
 void AlignmentTest::debug() {
@@ -47,6 +56,77 @@ void AlignmentTest::debug() {
     CORRADE_COMPARE(out.str(), "Text::Alignment::MiddleRightGlyphBounds Text::Alignment(0xab)\n");
 }
 
+void AlignmentTest::forDirection() {
+    /* For alignment that's neither Start nor End it's just a passthrough */
+    CORRADE_COMPARE(alignmentForDirection(
+        Alignment::BottomRightGlyphBounds,
+        LayoutDirection::HorizontalTopToBottom,
+        ShapeDirection::RightToLeft
+    ), Alignment::BottomRightGlyphBounds);
+    CORRADE_COMPARE(alignmentForDirection(
+        Alignment::MiddleLeftIntegral,
+        LayoutDirection::HorizontalTopToBottom,
+        ShapeDirection::RightToLeft
+    ), Alignment::MiddleLeftIntegral);
+    CORRADE_COMPARE(alignmentForDirection(
+        Alignment::TopCenter,
+        LayoutDirection::HorizontalTopToBottom,
+        ShapeDirection::LeftToRight
+    ), Alignment::TopCenter);
+
+    /* For Start / End it resolves based on ShapeDirection, keeping all extra
+       bits as well */
+    CORRADE_COMPARE(alignmentForDirection(
+        Alignment::TopStart,
+        LayoutDirection::HorizontalTopToBottom,
+        ShapeDirection::LeftToRight
+    ), Alignment::TopLeft);
+    CORRADE_COMPARE(alignmentForDirection(
+        Alignment::MiddleEndIntegral,
+        LayoutDirection::HorizontalTopToBottom,
+        ShapeDirection::LeftToRight
+    ), Alignment::MiddleRightIntegral);
+    CORRADE_COMPARE(alignmentForDirection(
+        Alignment::MiddleStartGlyphBoundsIntegral,
+        LayoutDirection::HorizontalTopToBottom,
+        ShapeDirection::RightToLeft
+    ), Alignment::MiddleRightGlyphBoundsIntegral);
+    CORRADE_COMPARE(alignmentForDirection(
+        Alignment::LineEndGlyphBounds,
+        LayoutDirection::HorizontalTopToBottom,
+        ShapeDirection::RightToLeft
+    ), Alignment::LineLeftGlyphBounds);
+
+    /* Unspecified ShapeDirection behaves same as LeftToRight */
+    CORRADE_COMPARE(alignmentForDirection(
+        Alignment::BottomStart,
+        LayoutDirection::HorizontalTopToBottom,
+        ShapeDirection::Unspecified
+    ), Alignment::BottomLeft);
+    CORRADE_COMPARE(alignmentForDirection(
+        Alignment::TopEndGlyphBounds,
+        LayoutDirection::HorizontalTopToBottom,
+        ShapeDirection::Unspecified
+    ), Alignment::TopRightGlyphBounds);
+}
+
+void AlignmentTest::forDirectionInvalid() {
+    CORRADE_SKIP_IF_NO_ASSERT();
+
+    std::ostringstream out;
+    Error redirectError{&out};
+    /* It should blow up also for alignments that don't use Start or End, for
+       consistency */
+    alignmentForDirection(Alignment::BottomCenter, LayoutDirection::VerticalRightToLeft, ShapeDirection::Unspecified);
+    alignmentForDirection(Alignment::MiddleCenterIntegral, LayoutDirection::HorizontalTopToBottom, ShapeDirection::TopToBottom);
+    alignmentForDirection(Alignment::MiddleCenterIntegral, LayoutDirection::HorizontalTopToBottom, ShapeDirection::BottomToTop);
+    CORRADE_COMPARE_AS(out.str(),
+        "Text::alignmentForDirection(): only Text::LayoutDirection::HorizontalTopToBottom is supported right now, got Text::LayoutDirection::VerticalRightToLeft\n"
+        "Text::alignmentForDirection(): Text::ShapeDirection::TopToBottom is not supported yet, sorry\n"
+        "Text::alignmentForDirection(): Text::ShapeDirection::BottomToTop is not supported yet, sorry\n",
+        TestSuite::Compare::String);
+}
+
 }}}}
 
 CORRADE_TEST_MAIN(Magnum::Text::Test::AlignmentTest)

src/Magnum/Text/Test/CMakeLists.txt

@@ -77,7 +77,7 @@ endif()
 corrade_add_test(TextAbstractShaperTest AbstractShaperTest.cpp
     LIBRARIES MagnumTextTestLib)
 
-corrade_add_test(TextAlignmentTest AlignmentTest.cpp LIBRARIES MagnumText)
+corrade_add_test(TextAlignmentTest AlignmentTest.cpp LIBRARIES MagnumTextTestLib)
 corrade_add_test(TextDirectionTest DirectionTest.cpp LIBRARIES MagnumText)
 corrade_add_test(TextFeatureTest FeatureTest.cpp LIBRARIES MagnumTextTestLib)
 corrade_add_test(TextRendererTest RendererTest.cpp LIBRARIES MagnumTextTestLib)

src/Magnum/Text/Test/RendererTest.cpp

@@ -122,62 +122,106 @@ const struct {
 const struct {
     TestSuite::TestCaseDescriptionSourceLocation name;
     Alignment alignment;
+    ShapeDirection shapeDirection;
     Vector2 offset;
 } RenderDataData[]{
     /* Not testing all combinations, just making sure that each horizontal,
        vertical, glyph bounds and integer variant is covered */
-    {"line left", Alignment::LineLeft,
+    {"line left",
+        Alignment::LineLeft, ShapeDirection::Unspecified,
         /* This is the default (0) value, thus should result in no shift */
         {}},
-    {"line left, glyph bounds", Alignment::LineLeftGlyphBounds,
+    {"line left, glyph bounds",
+        Alignment::LineLeftGlyphBounds, ShapeDirection::Unspecified,
         /* The first glyph has X offset of 2.5, which is subtracted */
         {-2.5f, 0.0f}},
-    {"top left", Alignment::TopLeft,
+    {"top left",
+        Alignment::TopLeft, ShapeDirection::Unspecified,
         /* Ascent is 4.5, scaled by 0.5 */
         {0.0f, -2.25f}},
-    {"top left, glyph bounds", Alignment::TopLeftGlyphBounds,
+    {"top left, glyph bounds",
+        Alignment::TopLeftGlyphBounds, ShapeDirection::Unspecified,
         /* Largest Y value is 10.5f */
         {-2.5f, -10.5f}},
-    {"top right", Alignment::TopRight,
+    {"top right",
+        Alignment::TopRight, ShapeDirection::Unspecified,
         /* Advances were 1, 2, 3, so 6 in total, ascent is 4.5; scaled by
            0.5 */
         {-3.0f, -2.25f}},
-    {"top right, glyph bounds", Alignment::TopRightGlyphBounds,
+    {"top right, glyph bounds",
+        Alignment::TopRightGlyphBounds, ShapeDirection::Unspecified,
         /* Basically subtracting the largest vertex value */
         {-12.5f, -10.5f}},
-    {"top center", Alignment::TopCenter,
+    {"top center",
+        Alignment::TopCenter, ShapeDirection::Unspecified,
         /* Advances were 1, 2, 3, so 6 in total, center is 3, scaled by 0.5 */
         {-1.5f, -2.25f}},
-    {"top center, integral", Alignment::TopCenterIntegral,
+    {"top center, integral",
+        Alignment::TopCenterIntegral, ShapeDirection::Unspecified,
         /* The Y shift isn't whole units but only X is rounded here */
         {-2.0f, -2.25f}},
-    {"top center, glyph bounds", Alignment::TopCenterGlyphBounds,
+    {"top center, glyph bounds",
+        Alignment::TopCenterGlyphBounds, ShapeDirection::Unspecified,
         {-7.5f, -10.5f}},
-    {"top center, glyph bounds, integral", Alignment::TopCenterGlyphBoundsIntegral,
+    {"top center, glyph bounds, integral",
+        Alignment::TopCenterGlyphBoundsIntegral, ShapeDirection::Unspecified,
         /* The Y shift isn't whole units but only X is rounded here */
         {-8.0f, -10.5f}},
-    {"middle left, glyph bounds", Alignment::MiddleLeftGlyphBounds,
+    {"middle left, glyph bounds",
+        Alignment::MiddleLeftGlyphBounds, ShapeDirection::Unspecified,
         {-2.5f, -7.125f}},
-    {"middle left, glyph bounds, integral", Alignment::MiddleLeftGlyphBoundsIntegral,
+    {"middle left, glyph bounds, integral",
+        Alignment::MiddleLeftGlyphBoundsIntegral, ShapeDirection::Unspecified,
         /* The X shift isn't whole units but only Y is rounded here */
         {-2.5f, -7.0f}},
-    {"middle center", Alignment::MiddleCenter,
+    {"middle center",
+        Alignment::MiddleCenter, ShapeDirection::Unspecified,
         {-1.5f, -0.5f}},
-    {"middle center, integral", Alignment::MiddleCenterIntegral,
+    {"middle center, integral",
+        Alignment::MiddleCenterIntegral, ShapeDirection::Unspecified,
         /* Rounding happens on both X and Y in this case */
         {-2.0f, -1.0f}},
-    {"middle center, glyph bounds", Alignment::MiddleCenterGlyphBounds,
+    {"middle center, glyph bounds",
+        Alignment::MiddleCenterGlyphBounds, ShapeDirection::Unspecified,
         /* Half size of the bounds quad */
         {-7.5f, -7.125f}},
-    {"middle center, glyph bounds, integral", Alignment::MiddleCenterGlyphBoundsIntegral,
+    {"middle center, glyph bounds, integral",
+        Alignment::MiddleCenterGlyphBoundsIntegral, ShapeDirection::Unspecified,
         {-8.0f, -7.0f}},
-    {"bottom left", Alignment::BottomLeft,
+    {"bottom left",
+        Alignment::BottomLeft, ShapeDirection::Unspecified,
         /* Descent is -2.5; scaled by 0.5 */
         {0.0f, 1.25f}},
-    {"bottom right", Alignment::BottomRight,
+    {"bottom right",
+        Alignment::BottomRight, ShapeDirection::Unspecified,
         {-3.0f, 1.25f}},
-    {"bottom right, glyph bounds", Alignment::BottomRightGlyphBounds,
+    {"bottom right, glyph bounds",
+        Alignment::BottomRightGlyphBounds, ShapeDirection::Unspecified,
         {-12.5f, -3.75f}},
+    {"line start, direction unspecified",
+        Alignment::LineStart, ShapeDirection::Unspecified,
+        {}}, /* Same as line left, thus no shift */
+    {"bottom start, LTR",
+        Alignment::BottomStart, ShapeDirection::LeftToRight,
+        {0.0f, 1.25f}}, /* Same as bottom left */
+    {"line end, RTL",
+        Alignment::LineEnd, ShapeDirection::RightToLeft,
+        {}}, /* Again same as line left, thus no shift */
+    {"line end, direction unspecified",
+        Alignment::LineEnd, ShapeDirection::Unspecified,
+        {-3.0f, 0.0f}}, /* Same as line right */
+    {"top end, LTR",
+        Alignment::TopEnd, ShapeDirection::LeftToRight,
+        {-3.0f, -2.25f}}, /* Same as top right */
+    {"line start, RTL",
+        Alignment::LineStart, ShapeDirection::RightToLeft,
+        {-3.0f, 0.0f}}, /* Same as line right */
+    {"line left, RTL",
+        Alignment::LineLeft, ShapeDirection::RightToLeft,
+        {}}, /* Line left with no change */
+    {"middle center, RTL",
+        Alignment::MiddleCenter, ShapeDirection::RightToLeft,
+        {-1.5f, -0.5f}}, /* Middle center with no change */
 };
 
 const struct {
@@ -303,12 +347,16 @@ RendererTest::RendererTest() {
 }
 
 struct TestShaper: AbstractShaper {
-    using AbstractShaper::AbstractShaper;
+    explicit TestShaper(AbstractFont& font, ShapeDirection direction): AbstractShaper{font}, _direction{direction} {}
 
     UnsignedInt doShape(Containers::StringView text, UnsignedInt, UnsignedInt, Containers::ArrayView<const FeatureRange>) override {
         return text.size();
     }
 
+    ShapeDirection doDirection() const override {
+        return _direction;
+    }
+
     void doGlyphIdsInto(const Containers::StridedArrayView1D<UnsignedInt>& ids) const override {
         for(UnsignedInt i = 0; i != ids.size(); ++i) {
             /* It just rotates between the three glyphs */
@@ -325,9 +373,12 @@ struct TestShaper: AbstractShaper {
             /* Offset Y and advance X is getting larger with every glyph,
                advance Y is flipping its sign with every glyph */
             offsets[i] = Vector2::yAxis(i + 1);
+            /* This is always to the right, independent of ShapeDirection */
             advances[i] = {Float(i + 1), i % 2 ? -0.5f : +0.5f};
         }
     }
+
+    ShapeDirection _direction;
 };
 
 struct TestFont: AbstractFont {
@@ -350,9 +401,11 @@ struct TestFont: AbstractFont {
     Vector2 doGlyphAdvance(UnsignedInt) override { return {}; }
 
     Containers::Pointer<AbstractShaper> doCreateShaper() override {
-        return Containers::pointer<TestShaper>(*this);
+        return Containers::pointer<TestShaper>(*this, direction);
     }
 
+    ShapeDirection direction = ShapeDirection::Unspecified;
+
     bool _opened = false;
 };
 
@@ -817,7 +870,11 @@ void RendererTest::alignLineInvalidDirection() {
     std::ostringstream out;
     Error redirectError{&out};
     alignRenderedLine({}, LayoutDirection::VerticalRightToLeft, Alignment::LineLeft, nullptr);
-    CORRADE_COMPARE(out.str(), "Text::alignRenderedLine(): only Text::LayoutDirection::HorizontalTopToBottom is supported right now, got Text::LayoutDirection::VerticalRightToLeft\n");
+    alignRenderedLine({}, LayoutDirection::HorizontalTopToBottom, Alignment::BottomEnd, nullptr);
+    CORRADE_COMPARE_AS(out.str(),
+        "Text::alignRenderedLine(): only Text::LayoutDirection::HorizontalTopToBottom is supported right now, got Text::LayoutDirection::VerticalRightToLeft\n"
+        "Text::alignRenderedLine(): Text::Alignment::BottomEnd has to be resolved to *Left / *Right before being passed to this function\n",
+        TestSuite::Compare::String);
 }
 
 void RendererTest::alignBlock() {
@@ -847,7 +904,11 @@ void RendererTest::alignBlockInvalidDirection() {
     std::ostringstream out;
     Error redirectError{&out};
     alignRenderedBlock({}, LayoutDirection::VerticalRightToLeft, Alignment::LineLeft, nullptr);
-    CORRADE_COMPARE(out.str(), "Text::alignRenderedBlock(): only Text::LayoutDirection::HorizontalTopToBottom is supported right now, got Text::LayoutDirection::VerticalRightToLeft\n");
+    alignRenderedBlock({}, LayoutDirection::HorizontalTopToBottom, Alignment::LineStartGlyphBounds, nullptr);
+    CORRADE_COMPARE_AS(out.str(),
+        "Text::alignRenderedBlock(): only Text::LayoutDirection::HorizontalTopToBottom is supported right now, got Text::LayoutDirection::VerticalRightToLeft\n"
+        "Text::alignRenderedBlock(): Text::Alignment::LineStartGlyphBounds has to be resolved to *Left / *Right before being passed to this function\n",
+        TestSuite::Compare::String);
 }
 
 template<class T> void RendererTest::glyphQuadIndices() {
@@ -909,6 +970,7 @@ void RendererTest::renderData() {
     setTestCaseDescription(data.name);
 
     TestFont font;
+    font.direction = data.shapeDirection;
     font.openFile({}, 0.5f);
     DummyGlyphCache cache = testGlyphCache(font);