GL3: Make GLES3 work on Raspberry Pi 4B

(older Raspberry Pi versions don't support OpenGL ES 3.0, only 2.0)

src/client/refresh/gl3/gl3_image.c

@@ -191,15 +191,11 @@ GL3_Upload32(unsigned *data, int width, int height, qboolean mipmap)
 {
 	qboolean res;
 
-	int samples;
-	int i, c;
-	byte *scan;
-	int comp;
-
-	c = width * height;
-	scan = ((byte *)data) + 3;
-	samples = gl3_solid_format;
-	comp = gl3_tex_solid_format;
+	int i;
+	int c = width * height;
+	byte *scan = ((byte *)data) + 3;
+	int comp = gl3_tex_solid_format;
+	int samples = gl3_solid_format;
 
 	for (i = 0; i < c; i++, scan += 4)
 	{

src/client/refresh/gl3/gl3_main.c

@@ -35,8 +35,11 @@
 #define DG_DYNARR_IMPLEMENTATION
 #include "header/DG_dynarr.h"
 
-
+#ifdef YQ2_GL3_GLES3
+  #define REF_VERSION "Yamagi Quake II OpenGL ES3 Refresher"
+#else
   #define REF_VERSION "Yamagi Quake II OpenGL3 Refresher"
+#endif
 
 refimport_t ri;
 

src/client/refresh/gl3/gl3_misc.c

@@ -125,7 +125,16 @@ void
 GL3_ScreenShot(void)
 {
 	int w=vid.width, h=vid.height;
-	byte *buffer = malloc(w*h*3);
+
+#ifdef YQ2_GL3_GLES
+	// My RPi4's GLES3 doesn't like GL_RGB, so use GL_RGBA with GLES
+	// TODO: we could convert the screenshot to RGB before writing
+	//       so the resulting file is smaller
+	static const int comps = 4;
+#else // Desktop GL
+	static const int comps = 3;
+#endif
+	byte *buffer = malloc(w*h*comps);
 
 	if (!buffer)
 	{
@@ -134,13 +143,13 @@ GL3_ScreenShot(void)
 	}
 
 	glPixelStorei(GL_PACK_ALIGNMENT, 1);
-	glReadPixels(0, 0, w, h, GL_RGB, GL_UNSIGNED_BYTE, buffer);
+	glReadPixels(0, 0, w, h, (comps == 4) ? GL_RGBA : GL_RGB, GL_UNSIGNED_BYTE, buffer);
 
 	// the pixels are now row-wise left to right, bottom to top,
 	// but we need them row-wise left to right, top to bottom.
 	// so swap bottom rows with top rows
 	{
-		size_t bytesPerRow = 3*w;
+		size_t bytesPerRow = comps*w;
 		YQ2_VLA(byte, rowBuffer, bytesPerRow);
 		byte *curRowL = buffer; // first byte of first row
 		byte *curRowH = buffer + bytesPerRow*(h-1); // first byte of last row
@@ -156,7 +165,7 @@ GL3_ScreenShot(void)
 		YQ2_VLAFREE(rowBuffer);
 	}
 
-	ri.Vid_WriteScreenshot(w, h, 3, buffer);
+	ri.Vid_WriteScreenshot(w, h, comps, buffer);
 
 	free(buffer);
 }

src/client/refresh/gl3/gl3_sdl.c

@@ -236,7 +236,11 @@ int GL3_PrepareForWindow(void)
 #endif
 
 	// Set GL context flags.
-	int contextFlags = SDL_GL_CONTEXT_FORWARD_COMPATIBLE_FLAG;
+	int contextFlags = 0;
+
+#ifndef YQ2_GL3_GLES // Desktop GL (at least RPi4 doesn't like this for GLES3)
+	contextFlags |= SDL_GL_CONTEXT_FORWARD_COMPATIBLE_FLAG;
+#endif
 
 	if (gl3_debugcontext && gl3_debugcontext->value)
 	{
@@ -347,7 +351,11 @@ int GL3_InitContext(void* win)
 
 		return false;
 	}
+#ifdef YQ2_GL3_GLES3
+	else if (GLVersion.major < 3)
+#else // Desktop GL
 	else if (GLVersion.major < 3 || (GLVersion.major == 3 && GLVersion.minor < 2))
+#endif
 	{
 		R_Printf(PRINT_ALL, "GL3_InitContext(): ERROR: glad only got GL version %d.%d!\n", GLVersion.major, GLVersion.minor);
 

src/client/refresh/gl3/header/local.h

@@ -94,10 +94,11 @@ enum {
 	GL3_ATTRIB_LIGHTFLAGS = 5  // uint, each set bit means "dyn light i affects this surface"
 };
 
-// TODO: do we need the following configurable?
-static const int gl3_solid_format = GL_RGB;
+// always using RGBA now, GLES3 on RPi4 doesn't work otherwise
+// and I think all modern GPUs prefer 4byte pixels over 3bytes
+static const int gl3_solid_format = GL_RGBA;
 static const int gl3_alpha_format = GL_RGBA;
-static const int gl3_tex_solid_format = GL_RGB;
+static const int gl3_tex_solid_format = GL_RGBA;
 static const int gl3_tex_alpha_format = GL_RGBA;
 
 extern unsigned gl3_rawpalette[256];

src/client/vid/glimp_sdl.c

@@ -217,6 +217,7 @@ CreateSDLWindow(int flags, int w, int h)
 	}
 	else
 	{
+		Com_Printf("Creating window failed: %s\n", SDL_GetError());
 		return false;
 	}