Discards fragments as early as possible.

This commit moves the `discard` instruction in the fragment shader to an earlier position to avoid performing calculations whose results are unused.

src/nanovg_gl.h

@@ -334,7 +334,7 @@ static void glnvg__blendFuncSeparate(GLNVGcontext* gl, const GLNVGblend* blend)
 		(gl->blendFunc.dstRGB != blend->dstRGB) ||
 		(gl->blendFunc.srcAlpha != blend->srcAlpha) ||
 		(gl->blendFunc.dstAlpha != blend->dstAlpha)) {
-		
+
 		gl->blendFunc = *blend;
 		glBlendFuncSeparate(blend->srcRGB, blend->dstRGB, blend->srcAlpha,blend->dstAlpha);
 	}
@@ -626,6 +626,7 @@ static int glnvg__renderCreate(void* uptr)
 		"	float scissor = scissorMask(fpos);\n"
 		"#ifdef EDGE_AA\n"
 		"	float strokeAlpha = strokeMask();\n"
+		"	if (strokeAlpha < strokeThr) discard;\n"
 		"#else\n"
 		"	float strokeAlpha = 1.0;\n"
 		"#endif\n"
@@ -665,9 +666,6 @@ static int glnvg__renderCreate(void* uptr)
 		"		color *= scissor;\n"
 		"		result = color * innerCol;\n"
 		"	}\n"
-		"#ifdef EDGE_AA\n"
-		"	if (strokeAlpha < strokeThr) discard;\n"
-		"#endif\n"
 		"#ifdef NANOVG_GL3\n"
 		"	outColor = result;\n"
 		"#else\n"