Text: add glyphQuadBounds().

For when one needs to get the rectangle for aligning with
Alignment::*GlyphBounds but doesn't want to generate the actual quads
just yet.

doc/changelog.dox

@@ -458,9 +458,10 @@ See also:
     @ref TextureTools::AtlasLandfill allowing more efficient and incremental
     glyph packing together with support for texture arrays
 -   New @ref Text::renderLineGlyphPositionsInto(),
-    @ref Text::renderGlyphQuadsInto(), @ref Text::alignRenderedLine(),
-    @ref Text::alignRenderedBlock() and @ref Text::renderGlyphQuadIndicesInto()
-    APIs providing low-level access to the text renderer building blocks
+    @ref Text::renderGlyphQuadsInto(), @ref Text::glyphQuadBounds(),
+    @ref Text::alignRenderedLine(), @ref Text::alignRenderedBlock() and
+    @ref Text::renderGlyphQuadIndicesInto() APIs providing low-level access to
+    the text renderer building blocks
 -   New @ref Text::glyphRangeForBytes() API for providing byte-to-glyph mapping
     for arbitrarily complex shapers using the output from
     @ref Text::AbstractShaper::glyphClustersInto()

src/Magnum/Text/Renderer.cpp

@@ -191,6 +191,28 @@ Range2D renderGlyphQuadsInto(const AbstractGlyphCache& cache, const Float scale,
     return renderGlyphQuadsInto(cache, scale, glyphPositions, glyphIds, vertexPositions, vertexTextureCoordinates, nullptr);
 }
 
+Range2D glyphQuadBounds(const AbstractGlyphCache& cache, const Float scale, const Containers::StridedArrayView1D<const Vector2>& glyphPositions, const Containers::StridedArrayView1D<const UnsignedInt>& glyphIds) {
+    CORRADE_ASSERT(glyphIds.size() == glyphPositions.size(),
+        "Text::glyphQuadBounds(): expected glyphIds and glyphPositions views to have the same size, got" << glyphIds.size() << "and" << glyphPositions.size(), {});
+
+    /* Direct views on the cache data */
+    const Containers::StridedArrayView1D<const Vector2i> cacheGlyphOffsets = cache.glyphOffsets();
+    const Containers::StridedArrayView1D<const Range2Di> cacheGlyphRectangles = cache.glyphRectangles();
+
+    /* Basically what renderGlyphQuadsInto() does above, but producing just the
+       rectangle */
+    Range2D rectangle;
+    for(std::size_t i = 0; i != glyphIds.size(); ++i) {
+        const UnsignedInt glyphId = glyphIds[i];
+        const Range2D quad = Range2D::fromSize(
+            glyphPositions[i] + Vector2{cacheGlyphOffsets[glyphId]}*scale,
+            Vector2{cacheGlyphRectangles[glyphId].size()}*scale);
+        rectangle = Math::join(rectangle, quad);
+    }
+
+    return rectangle;
+}
+
 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, {});

src/Magnum/Text/Renderer.h

@@ -27,7 +27,7 @@
 */
 
 /** @file
- * @brief Class @ref Magnum::Text::AbstractRenderer, typedef @ref Magnum::Text::Renderer2D, @ref Magnum::Text::Renderer3D, function @ref Magnum::Text::renderLineGlyphPositionsInto(), @ref Magnum::Text::renderGlyphQuadsInto(), @ref Magnum::Text::alignRenderedLine(), @ref Magnum::Text::alignRenderedBlock(), @ref Magnum::Text::renderGlyphQuadIndicesInto(), @ref Magnum::Text::glyphRangeForBytes()
+ * @brief Class @ref Magnum::Text::AbstractRenderer, typedef @ref Magnum::Text::Renderer2D, @ref Magnum::Text::Renderer3D, function @ref Magnum::Text::renderLineGlyphPositionsInto(), @ref Magnum::Text::renderGlyphQuadsInto(), @ref Magnum::Text::glyphQuadBounds(), @ref Magnum::Text::alignRenderedLine(), @ref Magnum::Text::alignRenderedBlock(), @ref Magnum::Text::renderGlyphQuadIndicesInto(), @ref Magnum::Text::glyphRangeForBytes()
  */
 
 #include "Magnum/Magnum.h"
@@ -155,6 +155,7 @@ overload to get just 2D texture coordinates out. Use the
 @ref renderGlyphQuadsInto(const AbstractGlyphCache&, Float, const Containers::StridedArrayView1D<const Vector2>&, const Containers::StridedArrayView1D<const UnsignedInt>&, const Containers::StridedArrayView1D<Vector2>&, const Containers::StridedArrayView1D<Vector2>&)
 overload if you already have cache-global glyph IDs. Use
 @ref renderGlyphQuadIndicesInto() to populate the corresponding index array.
+@see @ref glyphQuadBounds()
 */
 MAGNUM_TEXT_EXPORT Range2D renderGlyphQuadsInto(const AbstractFont& font, Float size, const AbstractGlyphCache& cache, const Containers::StridedArrayView1D<const Vector2>& glyphPositions, const Containers::StridedArrayView1D<const UnsignedInt>& fontGlyphIds, const Containers::StridedArrayView1D<Vector2>& vertexPositions, const Containers::StridedArrayView1D<Vector3>& vertexTextureCoordinates);
 
@@ -187,6 +188,7 @@ mapping from font-specific glyph IDs to cache-global IDs happens in this case.
 As with the above overload, to optimize memory use, it's possible to alias
 @p glyphPositions and @p glyphIds with @cpp vertexPositions.every(4) @ce and
 @cpp vertexTextureCoordinates.every(4) @ce.
+@see @ref AbstractGlyphCache::glyphIdsInto(), @ref glyphQuadBounds()
 */
 MAGNUM_TEXT_EXPORT Range2D renderGlyphQuadsInto(const AbstractGlyphCache& cache, Float scale, const Containers::StridedArrayView1D<const Vector2>& glyphPositions, const Containers::StridedArrayView1D<const UnsignedInt>& glyphIds, const Containers::StridedArrayView1D<Vector2>& vertexPositions, const Containers::StridedArrayView1D<Vector3>& vertexTextureCoordinates);
 
@@ -200,6 +202,29 @@ depth is @cpp 1 @ce.
 */
 MAGNUM_TEXT_EXPORT Range2D renderGlyphQuadsInto(const AbstractGlyphCache& cache, Float scale, const Containers::StridedArrayView1D<const Vector2>& glyphPositions, const Containers::StridedArrayView1D<const UnsignedInt>& glyphIds, const Containers::StridedArrayView1D<Vector2>& vertexPositions, const Containers::StridedArrayView1D<Vector2>& vertexTextureCoordinates);
 
+/**
+@brief Calculate glyph quad bounds from cache-global glyph IDs
+@param[in] cache                Glyph cache to query for glyph rectangles
+@param[in] scale                Size to render the glyphs at divided by size of
+    the input font
+@param[in] glyphPositions       Glyph positions coming from an earlier call to
+    @ref renderLineGlyphPositionsInto()
+@param[in] glyphIds             Cache-global glyph IDs
+@return Rectangle spanning the glyph quads
+@m_since_latest
+
+Returns the same rectangle as @ref renderGlyphQuadsInto(const AbstractGlyphCache&, Float, const Containers::StridedArrayView1D<const Vector2>&, const Containers::StridedArrayView1D<const UnsignedInt>&, const Containers::StridedArrayView1D<Vector2>&, const Containers::StridedArrayView1D<Vector3>&)
+but without actually generating the glyph quads. Use the returned value for
+@ref alignRenderedLine() with a `*GlyphBounds` @ref Alignment value.
+
+Note that, unlike with @ref renderGlyphQuadsInto(const AbstractFont&, Float, const AbstractGlyphCache&, const Containers::StridedArrayView1D<const Vector2>&, const Containers::StridedArrayView1D<const UnsignedInt>&, const Containers::StridedArrayView1D<Vector2>&, const Containers::StridedArrayView1D<Vector3>&),
+this function doesn't have an overload taking font-local glyph IDs, as it
+doesn't have any scratch space to store them. Use
+@ref AbstractGlyphCache::glyphIdsInto() instead to convert them to cache-global
+and then call this function with the result.
+*/
+MAGNUM_TEXT_EXPORT Range2D glyphQuadBounds(const AbstractGlyphCache& cache, Float scale, const Containers::StridedArrayView1D<const Vector2>& glyphPositions, const Containers::StridedArrayView1D<const UnsignedInt>& glyphIds);
+
 /**
 @brief Align a rendered line
 @param[in] lineRectangle    Rectangle spanning the whole line
@@ -223,9 +248,12 @@ If @p alignment isn't `*GlyphBounds`, this function should get glyph
 and @p lineRectangle being all rectangles returned by that function combined
 together with @ref Math::join().
 
-If @p alignment is `*GlyphBounds`, this function should get vertex @p positions
-for a whole line coming from @ref renderGlyphQuadsInto() and @p lineRectangle
-being all rectangles returned by that function combined together with
+If @p alignment is `*GlyphBounds`, this function should get glyph @p positions
+for the whole line coming from @ref renderLineGlyphPositionsInto() and a
+@p lineRectangle being generated with @ref glyphQuadBounds() from those
+positions. Alternatively, it should get vertex @p positions for a whole line
+coming from @ref renderGlyphQuadsInto() and @p lineRectangle being all
+rectangles returned by that function combined together with
 @ref Math::join().
 
 The @p positions are translated in one axis based on the @p inputRectangle and
@@ -312,8 +340,8 @@ Assuming @p clusters is a view containing cluster IDs returned from
 @ref AbstractShaper::glyphClustersInto() and @p begin and @p end are byte
 positions in the text passed to @ref AbstractShaper::shape() for which the
 cluster IDs were retrieved, returns a range in the glyph array that contains
-given range. Assumes that @p clusters are either monotonically non-dereasing or
-non-increasing.
+given range. Assumes that @p clusters are either monotonically non-decreasing
+or non-increasing.
 
 If @p clusters are empty or @p end is less or equal to all @p clusters, returns
 @cpp {0, 0} @ce. If @p begin is greater than all @p clusters are, both return

src/Magnum/Text/Test/RendererTest.cpp

@@ -62,6 +62,9 @@ struct RendererTest: TestSuite::Tester {
     void glyphQuads2D();
     void glyphQuads2DArrayGlyphCache();
 
+    void glyphQuadBounds();
+    void glyphQuadBoundsInvalidViewSizes();
+
     void alignLine();
     void alignLineInvalidDirection();
 
@@ -344,7 +347,10 @@ RendererTest::RendererTest() {
     addInstancedTests({&RendererTest::glyphQuads2D},
         Containers::arraySize(GlyphQuadsData));
 
-    addTests({&RendererTest::glyphQuads2DArrayGlyphCache});
+    addTests({&RendererTest::glyphQuads2DArrayGlyphCache,
+
+              &RendererTest::glyphQuadBounds,
+              &RendererTest::glyphQuadBoundsInvalidViewSizes});
 
     addInstancedTests({&RendererTest::alignLine},
         Containers::arraySize(AlignLineData));
@@ -877,6 +883,51 @@ void RendererTest::glyphQuads2DArrayGlyphCache() {
     CORRADE_COMPARE(out, "Text::renderGlyphQuadsInto(): can't use this overload with an array glyph cache\n");
 }
 
+void RendererTest::glyphQuadBounds() {
+    /* Input like in glyphQuads(), verifying just the output rectangle */
+
+    TestFont font;
+    font.openFile({}, 2.5f);
+    DummyGlyphCache cache = testGlyphCacheArray(font);
+
+    Vector2 glyphPositions[]{
+        {100.0f, 200.0f},
+        {103.0f, 202.0f},
+        {107.0f, 196.0f}
+    };
+    UnsignedInt glyphIds[]{
+        /* Glyph 0 is the cache-global invalid glyph */
+        1, 3, 2
+    };
+
+    /* The font is opened at 2.5, rendering at 1.25, so everything will be
+       scaled by 0.5 */
+    Range2D rectangle = Text::glyphQuadBounds(cache, 1.25f/2.5f, glyphPositions, glyphIds);
+    CORRADE_COMPARE(rectangle, (Range2D{{102.5f, 198.5f}, {114.5f, 210.0f}}));
+}
+
+void RendererTest::glyphQuadBoundsInvalidViewSizes() {
+    CORRADE_SKIP_IF_NO_ASSERT();
+
+    TestFont font;
+    font.openFile({}, 5.0f);
+    DummyGlyphCache cache{PixelFormat::R8Unorm, {20, 20}};
+    cache.addFont(96, &font);
+    Vector2 glyphPositions[4];
+    Vector2 glyphPositionsInvalid[5];
+    UnsignedInt glyphIds[4]{};
+    UnsignedInt glyphIdsInvalid[3];
+
+    Containers::String out;
+    Error redirectError{&out};
+    Text::glyphQuadBounds(cache, 2.0f, glyphPositions, glyphIdsInvalid);
+    Text::glyphQuadBounds(cache, 2.0f, glyphPositionsInvalid, glyphIds);
+    CORRADE_COMPARE_AS(out,
+        "Text::glyphQuadBounds(): expected glyphIds and glyphPositions views to have the same size, got 3 and 4\n"
+        "Text::glyphQuadBounds(): expected glyphIds and glyphPositions views to have the same size, got 4 and 5\n",
+        TestSuite::Compare::String);
+}
+
 void RendererTest::alignLine() {
     auto&& data = AlignLineData[testCaseInstanceId()];
     setTestCaseDescription(data.name);