Draw

#import "extra/draw"

Collection of simple 2D primitive rendering functions. Internally the module uses OpenGL core profile for rendering and is supposed to be used for simple games or quick prototyping.

The draw module is not supposed to be an OpenGL replacement, if you want to do some advanced rendering, use OpenGL directly.

Features

  • Rendering of colored 2D rectangles with rotation.
  • Rendering of textured 2D rectangles with rotation.
  • Text rendering.
  • PNG texture loading using png module.
  • TTF font loading using freetype2 module (subpixel and grayscale antialiasing).

Notes

  • Module does not handle window creation and system events. Use i.e. glfw to do it.
  • The module is not feature-complete and still under development, all missing/required functionality should be implemented in the future; current implementation is mainly used to demonstrate the language capabilities.

General desing

The draw API is based on switching the global context of rendering primitives (rectangles). In example to draw bunch of colored rectangles we must set the propper shader first:

using draw;
using glm;
set_shader_color(); // Prepare renderer for rendering of colored rectangles.

rect(10.f, 10.f, 100.f, 100.f, v4.{ 1.f, 0.f, 0.f, 1.f });
rect(200.f, 10.f, 100.f, 100.f, v4.{ 0.f, 1.f, 0.f, 1.f });
rect(400.f, 10.f, 100.f, 100.f, v4.{ 0.f, 0.f, 1.f, 1.f });

Internally each call to rect just appends the geometry caches; actual rendering is done when currenty used shader is changed or flush is called explicitly. This approach reduces count of required draw calls a bit.

See the example.

draw.init

init :: fn (viewport_width: s32, viewport_height: s32) Error

Draw library initialization must be called once before the module is used. The viewport_width and viewport_height defines the viewport size in current opengl context. These values are usually the same as the window size.

The terminate must be called when draw module is not needed anymore.

The current OpenGL context must be aready set, the minimal required OpenGL version is 3.3 "Core Profile". You can use i.e. glfw or similar tool to create window and propper OpenGL context.

The gl_init function is called internally.

Note

Window resizing is not supported right now.

File: draw.bl

draw.terminate

terminate :: fn ()

Release all resources used by the module. This should be called when the module is not needed anymore.

The gl_terminate function is called internally.

File: draw.bl

draw.clear_color

clear_color :: fn (color :: )  #inline

Fill the current frame buffer with color. This is usually called each frame.

File: draw.bl

draw.set_shader_color

set_shader_color :: fn ()  #inline

Prepare renderer for rendering colored rectangles. Each rectangle can use different color. This method is supposed to be called before rect or rect_centered.

File: draw.bl

draw.set_shader_texture

set_shader_texture :: fn (texture: *Texture)  #inline

Prepare renderer for rendering textured rectangles. This method is supposed to be called before rect or rect_centered (all rectangles will use the same texture).

File: draw.bl

draw.set_shader_font

set_shader_font :: fn (font: *Font)  #inline

Prepare the renderer for rendering of a text.

File: draw.bl

draw.rect

rect :: fn (position_x: f32, position_y: f32, width: f32, height: f32, color :: )  #inline

Draw a single colored rectangle or texture into the frame buffer.

File: draw.bl

draw.rect_centered

rect_centered :: fn (center_x: f32, center_y: f32, width: f32, height: f32, color :: )  #inline

Draw a single colored rectangle or texture into the frame buffer.

File: draw.bl

draw.rect_centered_rotated

rect_centered_rotated :: fn (center_x: f32, center_y: f32, width: f32, height: f32, angle_in_radians: f32, color :: )  #inline

Draw a single colored rectangle or texture with rotation into the frame buffer.

File: draw.bl

draw.text

text :: fn (position_x: f32, position_y: f32, text: string_view, text_color : glm.v4: , background_color : glm.v4: )

Draw text into the frame buffer.

File: draw.bl

draw.flush

flush :: fn ()  #inline

Immediately render all cached stuff into the frame buffer.

File: draw.bl

draw.TextureFormat

TextureFormat :: enum u8 {
    RGB = 3;
    RGBA = 4;
}

Texture channel distribution format.

File: draw.bl

draw.Texture

Texture :: struct {
    format: TextureFormat;
    bit_depth: u8;
    width: u32;
    height: u32;
    handle: GLuint;
 }

Texture representation in draw module.

Members

  • format - Texture channel distribution format.
  • bit_depth - Bit depth of each channel.
  • width - Texture image width.
  • height - Texture image height.

File: draw.bl

draw.texture_init

texture_init :: fn (texture: *Texture, directory: string_view, filename: string_view) Error

Load png texture from the directory/filename.

File: draw.bl

draw.texture_terminate

texture_terminate :: fn (texture: *Texture)

Release texture data.

File: draw.bl

draw.png_load_from_file

png_load_from_file :: fn (filepath: string_view, out_data: **u8, out_width: *u32, out_height: *u32, out_bit_depth: *u8, out_format: *TextureFormat) Error

Loads png image from filepath into out_data. The out_data shoud be released by free call on caller side.

File: draw.bl

draw.Font

Font :: struct {
    char_table: ;
    atlas: Texture;
    size: f32;
    height: f32;
    mode: FontAntialiasing;
 }

File: draw.bl

draw.GlyphInfo

GlyphInfo :: struct {
    ax: f32;
    ay: f32;
    bw: f32;
    bh: f32;
    bl: f32;
    bt: f32;
    tx: f32;
    ty: f32;
    bs: f32;
 }

File: draw.bl

draw.FontAntialiasing

FontAntialiasing :: enum {
    SUBPIXEL;
    ALPHA;
}

Fonts in draw module can be loaded in two antialiasing modes.

Variants

  • SUBPIXEL - Clear Type mode, rendered glyphs must be perfectly aligned to the display pixels and the background color must be known.

  • ALPHA - Gray scale alpha blending.

File: draw.bl

draw.font_default_char_set

font_default_char_set :: fn () []u32 #inline

Returns default ASCII character table.

File: draw.bl

draw.font_generate_char_set

font_generate_char_set :: fn (chars: string_view, out_set: *[..]u32)

Generate new character table based on input chars.

File: draw.bl

draw.font_init_at_size

font_init_at_size :: fn (font: *Font, directory: string_view, filename: string_view, size: s32, mode :: , char_set :: ) Error

Initialize new font from the 'TTF' file at directory/filename at required size. Custom char_set can be specified in case we need to render some non-ascii unicode characters. Each loaded font must be terminated by font_terminate.

File: draw.bl

draw.font_terminate

font_terminate :: fn (font: *Font)

Terminate loaded font.

File: draw.bl