testing bitmap font generation and draw using stb_truetype

engine/app.cpp

@@ -52,6 +52,26 @@ void App::init()
         "void main(){"
         "   frag = col;"
         "}";
+    static const char* shader_font_v =
+        "#version 150\n"
+        "uniform mat4 mvp;"
+        "uniform vec2 texoff;"
+        "uniform vec2 texsz;"
+        "in vec4 pos;"
+        "in vec2 uvs;"
+        "out vec2 uv;"
+        "void main(){"
+        "   uv = texoff + uvs * texsz;"
+        "   gl_Position = mvp * vec4(pos.xyz, 1.f);"
+        "}";
+    static const char* shader_font_f =
+        "#version 150\n"
+        "uniform sampler2D tex;"
+        "in vec2 uv;"
+        "out vec4 frag;"
+        "void main(){"
+        "   frag = texture(tex, uv.xy);"
+        "}";
 
 #ifdef _WIN32
     static CONSOLE_SCREEN_BUFFER_INFO info;
@@ -77,14 +97,33 @@ void App::init()
     layout.load("data/layout.xml");
     //layout["main"].update(width, height);
 
-    sampler.create();
+    sampler.create(GL_NEAREST);
     ShaderManager::create(kShader::Texture, shader_v, shader_f);
     ShaderManager::create(kShader::Color, shader_color_v, shader_color_f);
     ShaderManager::create(kShader::UVs, shader_v, shader_uv_f);
+    ShaderManager::create(kShader::Font, shader_font_v, shader_font_f);
     WidgetBorder::m_plane.create<1>(1, 1);
 
     if (!tex.load("data/uvs.jpg"))
         printf("error loading image\n");
+
+    FILE* font_file = fopen("C:\\Windows\\Fonts\\arial.ttf", "rb");
+    if (font_file)
+    {
+        fseek(font_file, 0, SEEK_END);
+        long sz = ftell(font_file);
+        auto data = std::make_unique<uint8_t[]>(sz);
+        fseek(font_file, 0, SEEK_SET);
+        int bytes = fread(data.get(), 1, sz, font_file);
+        int w = 512;
+        int h = 512;
+        int num_chars = 96;
+        auto bitmap = std::make_unique<uint8_t[]>(w*h);
+        chars.resize(num_chars);
+        int ret = stbtt_BakeFontBitmap(data.get(), 0, 50, bitmap.get(), w, h, 32, num_chars, chars.data());
+        font_tex.create(w, h, GL_RED, bitmap.get());
+    }
+    plane.create<1>(400, 400);
     
     glEnable(GL_TEXTURE_2D);
     glDisable(GL_DEPTH_TEST);
@@ -120,12 +159,6 @@ void App::update(float dt)
         layout[main_id].update(width, height);
     }
 
-    glActiveTexture(GL_TEXTURE0);
-    tex.bind();
-    sampler.bind(0);
-    ShaderManager::use(kShader::Texture);
-    ShaderManager::u_int(kShaderUniform::Tex, 0);
-
     glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
     glEnable(GL_SCISSOR_TEST);
     for (auto& n : layout[main_id])
@@ -138,7 +171,29 @@ void App::update(float dt)
         }
     }
     glDisable(GL_SCISSOR_TEST); 
-    tex.unbind();
+
+    glm::mat4 proj = glm::ortho(0.f, width, height, 0.f, -1.f, 1.f);
+    glm::mat4 tran = glm::translate(glm::vec3(200, 200, 0));
+
+    static int i = 0;
+    i = (i + 1) % 32;
+    auto c = chars["hgfrr56789opk0876ryuewighfcuisdbn"[i] - 32];
+    glm::vec2 a(c.x0, c.y0);
+    glm::vec2 b(c.x1, c.y1);
+    glm::vec2 s(512, 512);
+    glm::vec2 tof = a / s;
+    glm::vec2 tsz = (b - a) / s;
+
+    glActiveTexture(GL_TEXTURE0);
+    font_tex.bind();
+    sampler.bind(0);
+    ShaderManager::use(kShader::Font);
+    ShaderManager::u_int(kShaderUniform::Tex, 0);
+    ShaderManager::u_mat4(kShaderUniform::MVP, proj * tran);
+    ShaderManager::u_vec2(kShaderUniform::Tof, tof);
+    ShaderManager::u_vec2(kShaderUniform::Tsz, tsz);
+    plane.draw_fill();
+    font_tex.unbind();
     sampler.unbind();
 }