sokol: add sg_isvalid wrapper to gfx (#12081)

vlib/gg/image.c.v

@@ -6,8 +6,6 @@ import os
 import stbi
 import sokol.gfx
 
-fn C.sg_isvalid() bool
-
 // TODO return ?Image
 pub fn (mut ctx Context) create_image(file string) Image {
 	// println('\ncreate_image("$file")')
@@ -25,7 +23,7 @@ pub fn (mut ctx Context) create_image(file string) Image {
 			return img
 		}
 	}
-	if !C.sg_isvalid() {
+	if !gfx.is_valid() {
 		// Sokol is not initialized yet, add stbi object to a queue/cache
 		// ctx.image_queue << file
 		stb_img := stbi.load(file) or { return Image{} }
@@ -145,7 +143,7 @@ pub fn (mut img Image) update_pixel_data(buf &byte) {
 
 // TODO copypasta
 pub fn (mut ctx Context) create_image_with_size(file string, width int, height int) Image {
-	if !C.sg_isvalid() {
+	if !gfx.is_valid() {
 		// Sokol is not initialized yet, add stbi object to a queue/cache
 		// ctx.image_queue << file
 		stb_img := stbi.load(file) or { return Image{} }

vlib/sokol/gfx/gfx.c.v

@@ -18,6 +18,11 @@ pub fn shutdown() {
 	C.sg_shutdown()
 }
 
+[inline]
+pub fn is_valid() bool {
+	return C.sg_isvalid()
+}
+
 [inline]
 pub fn reset_state_cache() {
 	C.sg_reset_state_cache()

vlib/sokol/gfx/gfx_funcs.c.v

@@ -3,6 +3,7 @@ module gfx
 // setup and misc functions
 fn C.sg_setup(desc &C.sg_desc)
 fn C.sg_shutdown()
+fn C.sg_isvalid() bool
 fn C.sg_reset_state_cache()
 
 // resource creation, destruction and updating