Outrun on OpenGL: Fix weird purple highlight seen on some devices

mediump int is just not enough.

Common/GPU/ShaderWriter.cpp

@@ -264,6 +264,13 @@ void ShaderWriter::EndFSMain(const char *vec4_color_variable) {
 	C("}\n");
 }
 
+void ShaderWriter::HighPrecisionInt() {
+	if (ShaderLanguageIsOpenGL(lang_.shaderLanguage) && lang_.gles) {
+		C("precision highp int;\n");
+		C("precision highp uint;\n");
+	}
+}
+
 void ShaderWriter::DeclareTexture2D(const char *name, int binding) {
 	switch (lang_.shaderLanguage) {
 	case HLSL_D3D11:

Common/GPU/ShaderWriter.h

@@ -63,6 +63,9 @@ public:
 	// F: Formats into the buffer.
 	ShaderWriter &F(const char *format, ...);
 
+	// Useful for fragment shaders in GLES.
+	void HighPrecisionInt();
+
 	// Several of the shader languages ignore samplers, beware of that.
 	void DeclareSampler2D(const char *name, int binding);
 	void DeclareTexture2D(const char *name, int binding);

GPU/Common/ReinterpretFramebuffer.cpp

@@ -18,6 +18,8 @@ bool GenerateReinterpretFragmentShader(char *buffer, GEBufferFormat from, GEBuff
 
 	ShaderWriter writer(buffer, lang, ShaderStage::Fragment, nullptr, 0);
 
+	writer.HighPrecisionInt();
+
 	writer.DeclareSampler2D("samp", 0);
 	writer.DeclareTexture2D("tex", 0);