GPUShader: Add specialized widget base shader.

This vertex shader let us draw widgets with batches instead of imm calls.

source/blender/gpu/CMakeLists.txt

@@ -132,6 +132,7 @@ data_to_c_simple(shaders/gpu_shader_simple_lighting_smooth_color_alpha_frag.glsl
 data_to_c_simple(shaders/gpu_shader_flat_color_frag.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_flat_color_alpha_test_0_frag.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_2D_vert.glsl SRC)
+data_to_c_simple(shaders/gpu_shader_2D_widget_base_vert.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_2D_flat_color_vert.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_2D_line_dashed_uniform_color_vert.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_2D_line_dashed_frag.glsl SRC)

source/blender/gpu/GPU_shader.h

@@ -169,6 +169,8 @@ typedef enum GPUBuiltinShader {
 	GPU_SHADER_INSTANCE_VARIYING_COLOR_VARIYING_SIZE, /* Uniformly scaled */
 	GPU_SHADER_INSTANCE_VARIYING_COLOR_VARIYING_SCALE,
 	GPU_SHADER_INSTANCE_EDGES_VARIYING_COLOR,
+	/* specialized for widget drawing */
+	GPU_SHADER_2D_WIDGET_BASE,
 
 	GPU_SHADER_3D_INSTANCE_BONE_ENVELOPE_SOLID,
 	GPU_SHADER_3D_INSTANCE_BONE_ENVELOPE_WIRE,

source/blender/gpu/intern/gpu_shader.c

@@ -66,6 +66,7 @@ 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_2D_image_vert_glsl[];
 extern char datatoc_gpu_shader_2D_image_rect_vert_glsl[];
+extern char datatoc_gpu_shader_2D_widget_base_vert_glsl[];
 
 extern char datatoc_gpu_shader_3D_image_vert_glsl[];
 extern char datatoc_gpu_shader_image_frag_glsl[];
@@ -784,6 +785,9 @@ GPUShader *GPU_shader_get_builtin_shader(GPUBuiltinShader shader)
 		                                               datatoc_gpu_shader_flat_color_frag_glsl,
 		                                               datatoc_gpu_shader_instance_edges_variying_color_geom_glsl},
 
+		[GPU_SHADER_2D_WIDGET_BASE] = { datatoc_gpu_shader_2D_widget_base_vert_glsl,
+		                                datatoc_gpu_shader_2D_smooth_color_frag_glsl},
+
 		[GPU_SHADER_3D_INSTANCE_BONE_ENVELOPE_SOLID] = { datatoc_gpu_shader_instance_bone_envelope_solid_vert_glsl,
 		                                                 datatoc_gpu_shader_simple_lighting_frag_glsl },
 		[GPU_SHADER_3D_INSTANCE_BONE_ENVELOPE_WIRE] = { datatoc_gpu_shader_instance_bone_envelope_wire_vert_glsl,

source/blender/gpu/shaders/gpu_shader_2D_widget_base_vert.glsl

@@ -0,0 +1,88 @@
+/* 2 bits for corner */
+/* Attention! Not the same order as in UI_interface.h!
+ * Ordered by drawing order. */
+#define BOTTOM_LEFT 0u
+#define BOTTOM_RIGHT 1u
+#define TOP_RIGHT 2u
+#define TOP_LEFT 3u
+#define CNR_FLAG_RANGE ((1u << 2u) - 1u)
+
+/* 4bits for corner id */
+#define CORNER_VEC_OFS 2u
+#define CORNER_VEC_RANGE ((1u << 4u) - 1u)
+const vec2 cornervec[36] = vec2[36](
+	vec2(0.0, 1.0), vec2(0.02, 0.805), vec2(0.067, 0.617), vec2(0.169, 0.45), vec2(0.293, 0.293), vec2(0.45, 0.169), vec2(0.617, 0.076), vec2(0.805, 0.02), vec2(1.0, 0.0),
+	vec2(-1.0, 0.0), vec2(-0.805, 0.02), vec2(-0.617, 0.067), vec2(-0.45, 0.169), vec2(-0.293, 0.293), vec2(-0.169, 0.45), vec2(-0.076, 0.617), vec2(-0.02, 0.805), vec2(0.0, 1.0),
+	vec2(0.0, -1.0), vec2(-0.02, -0.805), vec2(-0.067, -0.617), vec2(-0.169, -0.45), vec2(-0.293, -0.293), vec2(-0.45, -0.169), vec2(-0.617, -0.076), vec2(-0.805, -0.02), vec2(-1.0, 0.0),
+	vec2(1.0, 0.0), vec2(0.805, -0.02), vec2(0.617, -0.067), vec2(0.45, -0.169), vec2(0.293, -0.293), vec2(0.169, -0.45), vec2(0.076, -0.617), vec2(0.02, -0.805), vec2(0.0, -1.0)
+);
+
+/* 4bits for jitter id */
+#define JIT_OFS 6u
+#define JIT_RANGE ((1u << 4u) - 1u)
+const vec2 jit[9] = vec2[9](
+	vec2( 0.468813, -0.481430), vec2(-0.155755, -0.352820),
+	vec2( 0.219306, -0.238501), vec2(-0.393286, -0.110949),
+	vec2(-0.024699,  0.013908), vec2( 0.343805,  0.147431),
+	vec2(-0.272855,  0.269918), vec2( 0.095909,  0.388710),
+	vec2( 0.0,  0.0)
+);
+
+/* 2bits for other flag */
+#define INNER_FLAG (1u << 10u) /* is inner vert */
+#define EMBOSS_FLAG (1u << 11u) /* is emboss vert */
+
+uniform mat4 ModelViewProjectionMatrix;
+
+uniform vec4 parameters[7];
+/* radi and rad per corner */
+#define recti parameters[0]
+#define rect parameters[1]
+#define radsi parameters[2].x
+#define rads parameters[2].y
+#define faci parameters[2].zw
+#define roundCorners parameters[3]
+#define color1 parameters[4]
+#define color2 parameters[5]
+#define shadeDir parameters[6].x
+
+in uint vflag;
+
+noperspective out vec4 finalColor;
+
+void main()
+{
+	uint cflag = vflag & CNR_FLAG_RANGE;
+	uint vofs = (vflag >> CORNER_VEC_OFS) & CORNER_VEC_RANGE;
+
+	vec2 v = cornervec[cflag * 9u + vofs];
+
+	bool is_inner = (vflag & INNER_FLAG) != 0.0;
+
+	/* Scale by corner radius */
+	v *= roundCorners[cflag] * ((is_inner) ? radsi : rads);
+
+	/* Position to corner */
+	vec4 rct = (is_inner) ? recti : rect;
+	if (cflag == BOTTOM_LEFT)
+		v += rct.xz;
+	else if (cflag == BOTTOM_RIGHT)
+		v += rct.yz;
+	else if (cflag == TOP_RIGHT)
+		v += rct.yw;
+	else /* (cflag == TOP_LEFT) */
+		v += rct.xw;
+
+	/* compute uv and color gradient */
+	vec2 uv = faci * (v - recti.xz);
+	float fac = clamp((shadeDir > 0.0) ? uv.y : uv.x, 0.0, 1.0);
+	finalColor = mix(color2, color1, fac);
+
+	bool is_emboss = (vflag & EMBOSS_FLAG) != 0.0;
+	v.y -= (is_emboss) ? 1.0f : 0.0;
+
+	/* Antialiasing offset */
+	v += jit[(vflag >> JIT_OFS) & JIT_RANGE];
+
+	gl_Position = ModelViewProjectionMatrix * vec4(v, 0.0, 1.0);
+}