Hookup mkxp to run under a OpenGL ES 2.0 context

README.md

@@ -58,7 +58,7 @@ The exception is boost, which is weird in that it still hasn't managed to pull o
 ### Supported image/audio formats
 These depend on the SDL auxiliary libraries. For maximum RGSS compliance, build SDL2_image with png/jpg support, and SDL_sound with oggvorbis/wav/mp3 support.
 
-To run mkxp, you should have a graphics card capable of at least **OpenGL 2.0** with an up-to-date driver installed.
+To run mkxp, you should have a graphics card capable of at least **OpenGL (ES) 2.0** with an up-to-date driver installed.
 
 ## Configuration
 

src/gl-fun.cpp

@@ -82,11 +82,24 @@ void initGLFunctions()
 	/* Determine GL version */
 	const char *ver = (const char*) gl.GetString(GL_VERSION);
 
+	const char *glesPrefix = "OpenGL ES ";
+	size_t glesPrefixN = strlen(glesPrefix);
+
+	bool gles = false;
+
+	if (!strncmp(ver, glesPrefix, glesPrefixN))
+	{
+		gles = true;
+		gl.glsles = true;
+
+		ver += glesPrefixN;
+	}
+
 	/* Assume single digit */
 	int glMajor = *ver - '0';
 
 	if (glMajor < 2)
-		throw EXC("At least OpenGL 2.0 is required");
+		throw EXC("At least OpenGL (ES) 2.0 is required");
 
 	BoostSet<std::string> ext;
 
@@ -95,43 +108,53 @@ void initGLFunctions()
 	else
 		parseExtensionsCompat(gl.GetString, ext);
 
-	// FIXME: Set based on GL kind
-	gl.unpack_subimage = true;
-	gl.npot_repeat = true;
-
 #define HAVE_EXT(_ext) ext.contains("GL_" #_ext)
 
 	/* FBO entrypoints */
-	if (!HAVE_EXT(ARB_framebuffer_object))
-	{
-		if (!(HAVE_EXT(EXT_framebuffer_object) && HAVE_EXT(EXT_framebuffer_blit)))
-			throw EXC("No FBO extensions available");
-
-#undef EXT_SUFFIX
-#define EXT_SUFFIX "EXT"
-		GL_FBO_FUN;
-	}
-	else
+	if (glMajor >= 3 || HAVE_EXT(ARB_framebuffer_object))
 	{
 #undef EXT_SUFFIX
 #define EXT_SUFFIX ""
 		GL_FBO_FUN;
+		GL_FBO_BLIT_FUN;
+	}
+	else if (gles && glMajor == 2)
+	{
+		GL_FBO_FUN;
+	}
+	else if (HAVE_EXT(EXT_framebuffer_object))
+	{
+#undef EXT_SUFFIX
+#define EXT_SUFFIX "EXT"
+		GL_FBO_FUN;
+
+		if (HAVE_EXT(EXT_framebuffer_blit))
+		{
+			GL_FBO_BLIT_FUN;
+		}
+	}
+	else
+	{
+		throw EXC("No FBO support available");
 	}
 
 	/* VAO entrypoints */
-	if (!HAVE_EXT(ARB_vertex_array_object))
+	if (HAVE_EXT(ARB_vertex_array_object) || glMajor >= 3)
+	{
+#undef EXT_SUFFIX
+#define EXT_SUFFIX ""
+		GL_VAO_FUN;
+	}
+	else if (HAVE_EXT(APPLE_vertex_array_object))
 	{
-		if (!HAVE_EXT(APPLE_vertex_array_object))
-			throw EXC("No VAO extensions available");
-
 #undef EXT_SUFFIX
 #define EXT_SUFFIX "APPLE"
 		GL_VAO_FUN;
 	}
-	else
+	else if (HAVE_EXT(OES_vertex_array_object))
 	{
 #undef EXT_SUFFIX
-#define EXT_SUFFIX ""
+#define EXT_SUFFIX "OES"
 		GL_VAO_FUN;
 	}
 
@@ -148,4 +171,11 @@ void initGLFunctions()
 #define EXT_SUFFIX "ARB"
 		GL_DEBUG_KHR_FUN;
 	}
+
+	/* Misc caps */
+	if (!gles || glMajor >= 3 || HAVE_EXT(EXT_unpack_subimage))
+		gl.unpack_subimage = true;
+
+	if (!gles || glMajor >= 3 || HAVE_EXT(OES_texture_npot))
+		gl.npot_repeat = true;
 }

src/gl-fun.h

@@ -119,7 +119,9 @@ typedef void (APIENTRYP PFNGLDEBUGMESSAGECALLBACKPROC) (GLDEBUGPROC callback, co
 	GL_FUN(DeleteFramebuffers, PFNGLDELETEFRAMEBUFFERSPROC) \
 	GL_FUN(BindFramebuffer, PFNGLBINDFRAMEBUFFERPROC) \
 	GL_FUN(FramebufferTexture2D, PFNGLFRAMEBUFFERTEXTURE2DPROC) \
-	GL_FUN(FramebufferRenderbuffer, PFNGLFRAMEBUFFERRENDERBUFFERPROC) \
+	GL_FUN(FramebufferRenderbuffer, PFNGLFRAMEBUFFERRENDERBUFFERPROC)
+
+#define GL_FBO_BLIT_FUN \
 	GL_FUN(BlitFramebuffer, PFNGLBLITFRAMEBUFFERPROC)
 
 #define GL_VAO_FUN \
@@ -138,9 +140,11 @@ struct GLFunctions
 
 	GL_20_FUN
 	GL_FBO_FUN
+	GL_FBO_BLIT_FUN
 	GL_VAO_FUN
 	GL_DEBUG_KHR_FUN
 
+	bool glsles;
 	bool unpack_subimage;
 	bool npot_repeat;
 

src/shader.cpp

@@ -25,6 +25,7 @@
 #include "exception.h"
 
 #include <assert.h>
+#include <string.h>
 #include <iostream>
 
 #include "../sprite.frag.xxd"
@@ -107,6 +108,34 @@ void Shader::unbind()
 	glState.program.set(0);
 }
 
+static const char *glesHeader = "precision mediump float;\n";
+static const size_t glesHeaderSize = strlen(glesHeader);
+
+static void setupShaderSource(GLuint shader,
+                              const unsigned char *src, int srcSize)
+{
+	GLuint shaderSrcN;
+	const GLchar *shaderSrc[2];
+	GLint shaderSrcSize[2];
+
+	if (gl.glsles)
+	{
+		shaderSrcN = 2;
+		shaderSrc[0] = glesHeader;
+		shaderSrc[1] = (const GLchar*) src;
+		shaderSrcSize[0] = glesHeaderSize;
+		shaderSrcSize[1] = srcSize;
+	}
+	else
+	{
+		shaderSrcN = 1;
+		shaderSrc[0] = (const GLchar*) src;
+		shaderSrcSize[0] = srcSize;
+	}
+
+	gl.ShaderSource(shader, shaderSrcN, shaderSrc, shaderSrcSize);
+}
+
 void Shader::init(const unsigned char *vert, int vertSize,
                   const unsigned char *frag, int fragSize,
                   const char *vertName, const char *fragName,
@@ -115,7 +144,7 @@ void Shader::init(const unsigned char *vert, int vertSize,
 	GLint success;
 
 	/* Compile vertex shader */
-	gl.ShaderSource(vertShader, 1, (const GLchar**) &vert, (const GLint*) &vertSize);
+	setupShaderSource(vertShader, vert, vertSize);
 	gl.CompileShader(vertShader);
 
 	gl.GetShaderiv(vertShader, GL_COMPILE_STATUS, &success);
@@ -129,7 +158,7 @@ void Shader::init(const unsigned char *vert, int vertSize,
 	}
 
 	/* Compile fragment shader */
-	gl.ShaderSource(fragShader, 1, (const GLchar**) &frag, (const GLint*) &fragSize);
+	setupShaderSource(fragShader, frag, fragSize);
 	gl.CompileShader(fragShader);
 
 	gl.GetShaderiv(fragShader, GL_COMPILE_STATUS, &success);