DRW: Add DRW_viewport_invert_size_get for more ease of use.

source/blender/draw/intern/DRW_render.h

@@ -429,6 +429,7 @@ void DRW_viewport_matrix_override_unset(DRWViewportMatrixType type);
 void DRW_viewport_matrix_override_unset_all(void);
 
 const float *DRW_viewport_size_get(void);
+const float *DRW_viewport_invert_size_get(void);
 const float *DRW_viewport_screenvecs_get(void);
 const float *DRW_viewport_pixelsize_get(void);
 bool DRW_viewport_is_persp_get(void);

source/blender/draw/intern/draw_manager.c

@@ -297,7 +297,12 @@ void DRW_engine_viewport_data_size_get(
 
 const float *DRW_viewport_size_get(void)
 {
-	return &DST.size[0];
+	return DST.size;
+}
+
+const float *DRW_viewport_invert_size_get(void)
+{
+	return DST.inv_size;
 }
 
 const float *DRW_viewport_screenvecs_get(void)
@@ -364,6 +369,8 @@ static void drw_viewport_var_init(void)
 		GPU_viewport_size_get(DST.viewport, size);
 		DST.size[0] = size[0];
 		DST.size[1] = size[1];
+		DST.inv_size[0] = 1.0f / size[0];
+		DST.inv_size[1] = 1.0f / size[1];
 
 		DefaultFramebufferList *fbl = (DefaultFramebufferList *)GPU_viewport_framebuffer_list_get(DST.viewport);
 		DST.default_framebuffer = fbl->default_fb;
@@ -393,6 +400,9 @@ static void drw_viewport_var_init(void)
 		DST.size[0] = 0;
 		DST.size[1] = 0;
 
+		DST.inv_size[0] = 0;
+		DST.inv_size[1] = 0;
+
 		DST.default_framebuffer = NULL;
 		DST.vmempool = NULL;
 	}

source/blender/draw/intern/draw_manager.h

@@ -278,6 +278,7 @@ typedef struct DRWManager {
 	GPUViewport *viewport;
 	struct GPUFrameBuffer *default_framebuffer;
 	float size[2];
+	float inv_size[2];
 	float screenvecs[2][3];
 	float pixsize;