font: string rendering

font.lua

@@ -0,0 +1,95 @@
+local _math = require "_math"
+local mat4 = _math.mat4
+
+local pixel_font_data = love.filesystem.newFileData("pixel_font.glsl")
+local vertex_font_data = love.filesystem.newFileData("vertex_font.glsl")
+local shader_font = love.graphics.newShader(pixel_font_data, vertex_font_data)
+
+local fonts = {
+   ter_6x12 = {
+      path = "font/terminus_128x64_6x12.data",
+      texture_width = 128,
+      texture_height = 64,
+      glyph_width = 6,
+      glyph_height = 12,
+   },
+   ter_8x16 = {
+      path = "font/terminus_128x128_8x16.data",
+      texture_width = 128,
+      texture_height = 128,
+      glyph_width = 8,
+      glyph_height = 16,
+   },
+   ter_10x18 = {
+      path = "font/terminus_256x128_10x18.data",
+      texture_width = 256,
+      texture_height = 128,
+      glyph_width = 10,
+      glyph_height = 18,
+   },
+   ter_12x24 = {
+      path = "font/terminus_256x128_12x24.data",
+      texture_width = 256,
+      texture_height = 128,
+      glyph_width = 12,
+      glyph_height = 24,
+   }
+}
+
+local load_font = function(desc)
+   local file_data = love.filesystem.newFileData(desc.path)
+   local image_data = love.image.newImageData(desc.texture_width, desc.texture_height, "r8", file_data)
+   local texture = love.graphics.newTexture(image_data)
+   texture:setFilter("nearest", "nearest")
+   local font = {
+      texture = texture,
+      texture_width = desc.texture_width,
+      texture_height = desc.texture_height,
+      glyph_width = desc.glyph_width,
+      glyph_height = desc.glyph_height,
+      stride = math.floor(desc.texture_width / desc.glyph_width),
+   }
+   return font
+end
+
+local glyph_coordinate = function(font, ord)
+   local c = ord - 32
+   local x = c % font.stride
+   local y = math.floor(c / font.stride)
+   return {x, y}
+end
+
+local glyph_transform = function(font, x, y)
+   local transform = (
+        mat4.scaling(font.glyph_width, font.glyph_height, 0)
+      * mat4.translation(x, -y, 0)
+      * mat4.scaling(2 / 1024, 2 / 1024, 0)
+      * mat4.translation(-1, 1, 0)
+   )
+   return transform
+end
+
+local draw_string = function(font, s, x, y)
+   love.graphics.setCanvas()
+   love.graphics.setShader(shader_font)
+   shader_font:send("texture_sampler", font.texture)
+   love.graphics.setDepthMode("always", false)
+   shader_font:send("cell", {font.glyph_width / font.texture_width, font.glyph_height / font.texture_height})
+
+   for i = 1, #s do
+      local c = s:byte(i)
+      if c ~= 32 then
+         shader_font:send("transform", "column", glyph_transform(font, x, y).data)
+         shader_font:send("glyph", glyph_coordinate(font, c))
+         love.graphics.drawFromShader(screen_index_buffer, 3 * 2, 1, 1)
+      end
+
+      x = x + font.glyph_width
+   end
+end
+
+return {
+   fonts = fonts,
+   load_font = load_font,
+   draw_string = draw_string,
+}

main.lua

@@ -16,6 +16,9 @@ local scene_noodle = require 'scene.noodle.noodle'
 local scene_sci_fi_ship = require 'scene.sci_fi_ship.sci_fi_ship'
 local scene_shadow_test = require 'scene.shadow_test.shadow_test'
 
+local font = require 'font'
+local terminus_font
+
 local scenes = {
    sci_fi_ship = {
       descriptor = scene_sci_fi_ship.descriptor,
@@ -80,6 +83,8 @@ function love.load(args)
    g_shadow_canvas = love.graphics.newCanvas(2048, 2048, {format = "r32f"})
 
    load_screen_shader()
+
+   terminus_font = font.load_font(font.fonts.ter_10x18)
 end
 
 local rotation = 0.0
@@ -128,4 +133,6 @@ function love.draw()
    -- love.graphics.setShader(screen_shader)
    -- screen_shader:send("g_sampler", g_shadow_canvas)
    -- love.graphics.drawFromShader(screen_index_buffer, 3 * 2, 1, 1)
+
+   font.draw_string(terminus_font, "asdf test 1234", 10, 10)
 end

pixel_font.glsl

@@ -0,0 +1,19 @@
+#pragma language glsl3
+
+layout (location = 0) out vec4 g_color;
+
+uniform sampler2D texture_sampler;
+
+in vec4 PixelTexture;
+
+uniform vec2 cell;
+uniform vec2 glyph;
+
+void pixelmain()
+{
+  vec4 sample = texture(texture_sampler, PixelTexture.xy * cell + cell * glyph);
+  float px = sample.x == 0.0 ? 0.0 : 1.0;
+
+  g_color = vec4(vec3(px), 1.0);
+  //g_color = vec4(1, 0, 0, 1.0);
+}

vertex_font.glsl

@@ -0,0 +1,21 @@
+#pragma language glsl3
+
+const vec2 vtx[4] = vec2[](vec2(-1.0,  1.0),  // tl
+                           vec2( 1.0,  1.0),  // tr
+                           vec2( 1.0, -1.0),  // br
+                           vec2(-1.0, -1.0)); // bl
+
+uniform mat4 transform;
+
+out vec4 PixelTexture;
+
+void vertexmain()
+{
+  vec2 vertex = vtx[gl_VertexID];
+
+  PixelTexture = vec4(vertex * vec2(0.5, -0.5) + 0.5, 0, 0);
+
+  vertex = vertex * vec2(0.5, 0.5) + vec2(0.5, -0.5);
+
+  love_Position = transform * vec4(vertex, 0.0, 1.0);
+}