sokol: type alias all sgl structs, support sgl_context (#13018)

vlib/sokol/sgl/sgl_structs.c.v

@@ -1,24 +1,47 @@
 module sgl
 
-// should be in a proper module
-pub enum SglError {
-	no_error
-	vertices_full
-	commands_full
-	stack_overflow
-	stack_underfloat
-}
+import sokol.gfx
 
-pub struct C.sgl_pipeline {
+[typedef]
+struct C.sgl_pipeline {
 	id u32
 }
 
-pub struct C.sgl_desc_t {
+pub type Pipeline = C.sgl_pipeline
+
+[typedef]
+struct C.sgl_context {
+	id u32
+}
+
+pub type Context = C.sgl_context
+
+// ContextDesc
+//
+// Describes the initialization parameters of a rendering context.
+// Creating additional contexts is useful if you want to render
+// in separate sokol-gfx passes.
+// ContextDesc is sgl_context_desc_t
+pub type ContextDesc = C.sgl_context_desc_t
+
+[typedef]
+struct C.sgl_context_desc_t {
+	max_vertices int // default: 64k
+	max_commands int // default: 16k
+	color_format gfx.PixelFormat // C.sg_pixel_format
+	depth_format gfx.PixelFormat // C.sg_pixel_format
+	sample_count int
+}
+
+pub type Desc = C.sgl_desc_t
+
+[typedef]
+struct C.sgl_desc_t {
 	max_vertices       int // size for vertex buffer
 	max_commands       int // size of uniform- and command-buffers
 	pipeline_pool_size int // size of the internal pipeline pool, default is 64
-	color_format       C.sg_pixel_format
-	depth_format       C.sg_pixel_format
+	color_format       gfx.PixelFormat // C.sg_pixel_format
+	depth_format       gfx.PixelFormat // C.sg_pixel_format
 	sample_count       int
-	face_winding       C.sg_face_winding // default front face winding is CCW
+	face_winding       gfx.FaceWinding // C.sg_face_winding // default front face winding is CCW
 }