Text: add cache-related assertions to the AbstractRenderer constructor.

So it's nicer to users and doesn't fire only later during .render().

src/Magnum/Text/Renderer.cpp

@@ -1974,6 +1974,14 @@ AbstractRenderer::AbstractRenderer(AbstractFont& font, const AbstractGlyphCache&
     }
     #endif
 
+    /* These two are done in renderVerticesInternal() as well, but it makes
+       sense to verify the same here already, not only once .render() is
+       called */
+    CORRADE_ASSERT(cache.size().z() == 1,
+        "Text::AbstractRenderer: array glyph caches are not supported", );
+    CORRADE_ASSERT(cache.findFont(font),
+        "Text::AbstractRenderer: font not found among" << cache.fontCount() << "fonts in passed glyph cache", );
+
     /* Vertex buffer configuration depends on dimension count, done in subclass */
     _mesh.setPrimitive(MeshPrimitive::Triangles);
 }

src/Magnum/Text/Renderer.h

@@ -1664,6 +1664,9 @@ template<UnsignedInt dimensions> class MAGNUM_TEXT_EXPORT BasicRenderer: public
          * @param cache         Glyph cache
          * @param size          Font size
          * @param alignment     Text alignment
+         *
+         * Expects that @p font is present in @p cache and that @p cache isn't
+         * an array.
          */
         explicit BasicRenderer(AbstractFont& font, const AbstractGlyphCache& cache, Float size, Alignment alignment = Alignment::LineLeft);
         BasicRenderer(AbstractFont&, AbstractGlyphCache&&, Float, Alignment alignment = Alignment::LineLeft) = delete; /**< @overload */

src/Magnum/Text/Test/RendererGLTest.cpp

@@ -81,6 +81,9 @@ struct RendererGLTest: GL::OpenGLTester {
     void renderMeshIndexType();
     void mutableText();
 
+    void arrayGlyphCache();
+    void fontNotFoundInCache();
+
     private:
         PluginManager::Manager<Trade::AbstractImporter> _manager{"nonexistent"};
 
@@ -219,7 +222,10 @@ RendererGLTest::RendererGLTest() {
 
     addTests({&RendererGLTest::renderMesh,
               &RendererGLTest::renderMeshIndexType,
-              &RendererGLTest::mutableText});
+              &RendererGLTest::mutableText,
+
+              &RendererGLTest::arrayGlyphCache,
+              &RendererGLTest::fontNotFoundInCache});
 
     /* Load the plugins directly from the build tree. Otherwise they're either
        static and already loaded or not present in the build tree */
@@ -1069,6 +1075,53 @@ void RendererGLTest::mutableText() {
     #endif
 }
 
+void RendererGLTest::arrayGlyphCache() {
+    CORRADE_SKIP_IF_NO_ASSERT();
+
+    TestFont font;
+    font.openFile({}, 0.5f);
+    struct: AbstractGlyphCache {
+        using AbstractGlyphCache::AbstractGlyphCache;
+
+        GlyphCacheFeatures doFeatures() const override { return {}; }
+    } cache{PixelFormat::R8Unorm, {100, 100, 3}};
+
+    GL::Buffer buffer;
+
+    Containers::String out;
+    Error redirectError{&out};
+    Renderer2D::render(font, cache, 1.0f, "", buffer, buffer, GL::BufferUsage::StaticDraw);
+    Renderer2D{font, cache, 1.0f};
+    CORRADE_COMPARE(out,
+        "Text::Renderer: array glyph caches are not supported\n"
+        "Text::AbstractRenderer: array glyph caches are not supported\n");
+}
+
+void RendererGLTest::fontNotFoundInCache() {
+    CORRADE_SKIP_IF_NO_ASSERT();
+
+    TestFont font;
+    font.openFile({}, 0.5f);
+
+    struct: AbstractGlyphCache {
+        using AbstractGlyphCache::AbstractGlyphCache;
+
+        GlyphCacheFeatures doFeatures() const override { return {}; }
+    } cache{PixelFormat::R8Unorm, {100, 100}};
+    cache.addFont(34);
+    cache.addFont(25);
+
+    GL::Buffer buffer;
+
+    Containers::String out;
+    Error redirectError{&out};
+    Renderer2D::render(font, cache, 1.0f, "", buffer, buffer, GL::BufferUsage::StaticDraw);
+    Renderer2D{font, cache, 1.0f};
+    CORRADE_COMPARE(out,
+        "Text::Renderer: font not found among 2 fonts in passed glyph cache\n"
+        "Text::AbstractRenderer: font not found among 2 fonts in passed glyph cache\n");
+}
+
 }}}}
 
 CORRADE_TEST_MAIN(Magnum::Text::Test::RendererGLTest)