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More efficient OpenGL font loading

--- a/src/Backends/Rendering/OpenGL2.cpp

+++ b/src/Backends/Rendering/OpenGL2.cpp

@@ -326,8 +326,10 @@

 	if (glyph == NULL)

 		return NULL;

-	unsigned char *buffer = (unsigned char*)malloc(width * height * 4);

+	const int destination_pitch = (width + 3) & ~3;	// Round up to the nearest 4 (OpenGL needs this)

+	unsigned char *buffer = (unsigned char*)malloc(destination_pitch * height);

+

 	if (buffer == NULL)

 	{

 		free(glyph);

@@ -342,13 +344,10 @@

 			for (unsigned int y = 0; y < height; ++y)

 			{

 				const unsigned char *source_pointer = pixels + y * pitch;

-				unsigned char *destination_pointer = buffer + y * width * 4;

+				unsigned char *destination_pointer = buffer + y * destination_pitch;

 				for (unsigned int x = 0; x < width; ++x)

 				{

-					*destination_pointer++ = 0xFF;

-					*destination_pointer++ = 0xFF;

-					*destination_pointer++ = 0xFF;

 					*destination_pointer++ = (unsigned char)(pow((double)*source_pointer++ / (total_greys - 1), 1.0 / 1.8) * 255.0);

 				}

 			}

@@ -359,13 +358,10 @@

 			for (unsigned int y = 0; y < height; ++y)

 			{

 				const unsigned char *source_pointer = pixels + y * pitch;

-				unsigned char *destination_pointer = buffer + y * width * 4;

+				unsigned char *destination_pointer = buffer + y * destination_pitch;

 				for (unsigned int x = 0; x < width; ++x)

 				{

-					*destination_pointer++ = 0xFF;

-					*destination_pointer++ = 0xFF;

-					*destination_pointer++ = 0xFF;

 					*destination_pointer++ = *source_pointer++ ? 0xFF : 0;

 				}

 			}

@@ -375,7 +371,7 @@

 	glGenTextures(1, &glyph->texture_id);

 	glBindTexture(GL_TEXTURE_2D, glyph->texture_id);

-	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, buffer);

+	glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA8, width, height, 0, GL_ALPHA, GL_UNSIGNED_BYTE, buffer);

 	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

 	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);