template<UnsignedInt dimensions>

Magnum::Text::Renderer class

Usage

Immutable text (e.g. menu items, credits) can be simply rendered using static methods, returning result either as data arrays or as fully configured mesh. The text can be then drawn as usual by configuring the shader and drawing the mesh:

/* Font instance, received from a plugin manager */
std::unique_ptr<Text::AbstractFont> font;

/* Configured glyph cache */
Text::GlyphCache cache{Vector2i{512}};
font->fillGlyphCache(cache, "abcdefghijklmnopqrstuvwxyz"
                            "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                            "0123456789?!:;,. ");

Shaders::Vector2D shader;
GL::Buffer vertexBuffer, indexBuffer;
GL::Mesh mesh;

/* Render the text, centered */
std::tie(mesh, std::ignore) = Text::Renderer2D::render(*font, cache, 0.15f,
    "Hello World!", vertexBuffer, indexBuffer, GL::BufferUsage::StaticDraw,
    Text::Alignment::LineCenter);

/* Draw the text on the screen */
shader.setTransformationProjectionMatrix(projectionMatrix)
    .setColor(0xffffff_rgbf)
    .bindVectorTexture(cache.texture());
mesh.draw(shader);

See render(AbstractFont&, const GlyphCache&, Float, const std::string&, Alignment) and render(AbstractFont&, const GlyphCache&, Float, const std::string&, GL::Buffer&, GL::Buffer&, GL::BufferUsage, Alignment) for more information.

While this method is sufficient for one-shot rendering of static texts, for mutable texts (e.g. FPS counters, chat messages) there is another approach that doesn't recreate everything on each text change:

/* Initialize the renderer and reserve memory for enough glyphs */
Text::Renderer2D renderer{*font, cache, 0.15f, Text::Alignment::LineCenter};
renderer.reserve(32, GL::BufferUsage::DynamicDraw, GL::BufferUsage::StaticDraw);

/* Update the text occasionally */
renderer.render("Hello World Countdown: 10");

/* Draw the text on the screen */
shader.setTransformationProjectionMatrix(projectionMatrix)
    .setColor(0xffffff_rgbf)
    .bindVectorTexture(cache.texture());
renderer.mesh().draw(shader);

Required OpenGL functionality

Mutable text rendering requires ARB_map_buffer_range on desktop OpenGL (also part of OpenGL ES 3.0). If EXT_map_buffer_range is not available in ES 2.0, at least OES_mapbuffer must be supported for asynchronous buffer updates. There is no similar extension in WebGL, thus plain (and slow) buffer updates are used there.

Base classes

class AbstractRenderer

Base for text renderers.

Public static functions

static auto render(AbstractFont& font, const GlyphCache& cache, Float size, const std::string& text, GL::Buffer& vertexBuffer, GL::Buffer& indexBuffer, GL::BufferUsage usage, Alignment alignment = Alignment::LineLeft) -> std::tuple<GL::Mesh, Range2D>

Render text.

Constructors, destructors, conversion operators

Renderer(AbstractFont& font, const GlyphCache& cache, Float size, Alignment alignment = Alignment::LineLeft) explicit

Constructor.

Renderer(AbstractFont&, GlyphCache&&, Float, Alignment alignment = Alignment::LineLeft) deleted

Function documentation