OpenGL: add simple shaders for 2D drawing

The first two of several new simple built-in shaders (will test these
before adding more). These are intended for the new immediate mode API,
but you can use them just like any built-in GPUShader.

Due to limitations on different platforms, shaders need to work with
GLSL versions 120, 130 and 150. Final Blender 2.8 will be pure #version
150.

source/blender/gpu/CMakeLists.txt

@@ -100,6 +100,11 @@ set(SRC
 	intern/gpu_private.h
 )
 
+data_to_c_simple(shaders/gpu_shader_2D_uniform_color_vert.glsl SRC)
+data_to_c_simple(shaders/gpu_shader_2D_uniform_color_frag.glsl SRC)
+data_to_c_simple(shaders/gpu_shader_2D_smooth_color_vert.glsl SRC)
+data_to_c_simple(shaders/gpu_shader_2D_smooth_color_frag.glsl SRC)
+
 data_to_c_simple(shaders/gpu_shader_geometry.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_smoke_frag.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_smoke_vert.glsl SRC)

source/blender/gpu/GPU_shader.h

@@ -89,6 +89,10 @@ typedef enum GPUBuiltinShader {
 	GPU_SHADER_SEP_GAUSSIAN_BLUR = 1,
 	GPU_SHADER_SMOKE             = 2,
 	GPU_SHADER_SMOKE_FIRE        = 3,
+
+	/* for simple drawing */
+	GPU_SHADER_2D_UNIFORM_COLOR,
+	GPU_SHADER_2D_SMOOTH_COLOR,
 } GPUBuiltinShader;
 
 GPUShader *GPU_shader_get_builtin_shader(GPUBuiltinShader shader);

source/blender/gpu/intern/gpu_shader.c

@@ -45,6 +45,11 @@
 #define MAX_EXT_DEFINE_LENGTH 1024
 
 /* Non-generated shaders */
+extern char datatoc_gpu_shader_2D_uniform_color_vert_glsl[];
+extern char datatoc_gpu_shader_2D_uniform_color_frag_glsl[];
+extern char datatoc_gpu_shader_2D_smooth_color_vert_glsl[];
+extern char datatoc_gpu_shader_2D_smooth_color_frag_glsl[];
+
 extern char datatoc_gpu_shader_smoke_vert_glsl[];
 extern char datatoc_gpu_shader_smoke_frag_glsl[];
 extern char datatoc_gpu_shader_vsm_store_vert_glsl[];
@@ -69,6 +74,9 @@ static struct GPUShadersGlobal {
 		GPUShader *smoke_fire;
 		/* cache for shader fx. Those can exist in combinations so store them here */
 		GPUShader *fx_shaders[MAX_FX_SHADERS * 2];
+		/* for simple drawing */
+		GPUShader *uniform_color_2D;
+		GPUShader *smooth_color_2D;
 	} shaders;
 } GG = {{NULL}};
 
@@ -622,6 +630,22 @@ GPUShader *GPU_shader_get_builtin_shader(GPUBuiltinShader shader)
 				        NULL, NULL, "#define USE_FIRE;\n", 0, 0, 0);
 			retval = GG.shaders.smoke_fire;
 			break;
+		case GPU_SHADER_2D_UNIFORM_COLOR:
+			if (!GG.shaders.uniform_color_2D)
+				GG.shaders.uniform_color_2D = GPU_shader_create(
+				        datatoc_gpu_shader_2D_uniform_color_vert_glsl,
+				        datatoc_gpu_shader_2D_uniform_color_frag_glsl,
+				        NULL, NULL, NULL, 0, 0, 0);
+			retval = GG.shaders.uniform_color_2D;
+			break;
+		case GPU_SHADER_2D_SMOOTH_COLOR:
+			if (!GG.shaders.smooth_color_2D)
+				GG.shaders.smooth_color_2D = GPU_shader_create(
+				        datatoc_gpu_shader_2D_smooth_color_vert_glsl,
+				        datatoc_gpu_shader_2D_smooth_color_frag_glsl,
+				        NULL, NULL, NULL, 0, 0, 0);
+			retval = GG.shaders.smooth_color_2D;
+			break;
 	}
 
 	if (retval == NULL)
@@ -733,6 +757,16 @@ void GPU_shader_free_builtin_shaders(void)
 		GG.shaders.smoke_fire = NULL;
 	}
 
+	if (GG.shaders.uniform_color_2D) {
+		GPU_shader_free(GG.shaders.uniform_color_2D);
+		GG.shaders.uniform_color_2D = NULL;
+	}
+
+	if (GG.shaders.smooth_color_2D) {
+		GPU_shader_free(GG.shaders.smooth_color_2D);
+		GG.shaders.smooth_color_2D = NULL;
+	}
+
 	for (i = 0; i < 2 * MAX_FX_SHADERS; ++i) {
 		if (GG.shaders.fx_shaders[i]) {
 			GPU_shader_free(GG.shaders.fx_shaders[i]);

source/blender/gpu/shaders/gpu_shader_2D_smooth_color_frag.glsl

@@ -0,0 +1,13 @@
+
+#if __VERSION__ == 120
+  varying vec4 finalColor;
+  #define fragColor gl_FragColor
+#else
+  noperspective in vec4 finalColor;
+  out vec4 fragColor;
+#endif
+
+void main()
+{
+	fragColor = finalColor;
+}

source/blender/gpu/shaders/gpu_shader_2D_smooth_color_vert.glsl

@@ -0,0 +1,18 @@
+
+#if __VERSION__ == 120
+  attribute vec2 pos;
+  attribute vec4 color;
+
+  varying vec4 finalColor;
+#else
+  in vec2 pos;
+  in vec4 color;
+
+  noperspective out vec4 finalColor;
+#endif
+
+void main()
+{
+	gl_Position = gl_ModelViewMatrix * vec4(pos, 0.0, 1.0);
+	finalColor = color;
+}

source/blender/gpu/shaders/gpu_shader_2D_uniform_color_frag.glsl

@@ -0,0 +1,13 @@
+
+uniform vec4 color;
+
+#if __VERSION__ == 120
+  #define fragColor gl_FragColor
+#else
+  out vec4 fragColor;
+#endif
+
+void main()
+{
+	fragColor = color;
+}

source/blender/gpu/shaders/gpu_shader_2D_uniform_color_vert.glsl

@@ -0,0 +1,11 @@
+
+#if __VERSION__ == 120
+  attribute vec2 pos;
+#else
+  in vec2 pos;
+#endif
+
+void main()
+{
+	gl_Position = gl_ModelViewMatrix * vec4(pos, 0.0, 1.0);
+}