video_core: Make the OpenGL renderer work on GL 2.0+ and GLES 2.0+

src/video_core/renderer_opengl/gl_shader_util.cpp

@@ -10,7 +10,7 @@
 
 namespace ShaderUtil {
 
-GLuint LoadShaders(const char* vertex_shader, const char* fragment_shader) {
+GLuint LoadShaders(const char* glsl_header, const char* vertex_shader, const char* fragment_shader) {
 
     // Create the shaders
     GLuint vertex_shader_id = glCreateShader(GL_VERTEX_SHADER);
@@ -22,7 +22,8 @@ GLuint LoadShaders(const char* vertex_shader, const char* fragment_shader) {
     // Compile Vertex Shader
     LOG_DEBUG(Render_OpenGL, "Compiling vertex shader...");
 
-    glShaderSource(vertex_shader_id, 1, &vertex_shader, nullptr);
+    const char* vertex_source[2] = {glsl_header, vertex_shader};
+    glShaderSource(vertex_shader_id, 2, vertex_source, nullptr);
     glCompileShader(vertex_shader_id);
 
     // Check Vertex Shader
@@ -42,7 +43,8 @@ GLuint LoadShaders(const char* vertex_shader, const char* fragment_shader) {
     // Compile Fragment Shader
     LOG_DEBUG(Render_OpenGL, "Compiling fragment shader...");
 
-    glShaderSource(fragment_shader_id, 1, &fragment_shader, nullptr);
+    const char* fragment_source[2] = {glsl_header, fragment_shader};
+    glShaderSource(fragment_shader_id, 2, fragment_source, nullptr);
     glCompileShader(fragment_shader_id);
 
     // Check Fragment Shader

src/video_core/renderer_opengl/gl_shader_util.h

@@ -8,6 +8,6 @@
 
 namespace ShaderUtil {
 
-GLuint LoadShaders(const char* vertex_file_path, const char* fragment_file_path);
+GLuint LoadShaders(const char* glsl_header, const char* vertex_shader, const char* fragment_shader);
 
 }

src/video_core/renderer_opengl/gl_shaders.h

@@ -7,38 +7,40 @@
 namespace GLShaders {
 
 const char g_vertex_shader[] = R"(
-#version 150 core
+#if GL_ES && __VERSION__ >= 300 || !GL_ES && __VERSION__ >= 130
+#define attribute in
+#define varying out
+#endif
 
-in vec2 vert_position;
-in vec2 vert_tex_coord;
-out vec2 frag_tex_coord;
+attribute mediump vec2 vert_position;
+attribute mediump vec2 vert_tex_coord;
+varying mediump vec2 frag_tex_coord;
 
-// This is a truncated 3x3 matrix for 2D transformations:
-// The upper-left 2x2 submatrix performs scaling/rotation/mirroring.
-// The third column performs translation.
-// The third row could be used for projection, which we don't need in 2D. It hence is assumed to
-// implicitly be [0, 0, 1]
-uniform mat3x2 modelview_matrix;
+uniform mat3 modelview_matrix;
 
 void main() {
-    // Multiply input position by the rotscale part of the matrix and then manually translate by
-    // the last column. This is equivalent to using a full 3x3 matrix and expanding the vector
-    // to `vec3(vert_position.xy, 1.0)`
-    gl_Position = vec4(mat2(modelview_matrix) * vert_position + modelview_matrix[2], 0.0, 1.0);
+    gl_Position = vec4(modelview_matrix * vec3(vert_position, 1.0), 1.0);
     frag_tex_coord = vert_tex_coord;
 }
 )";
 
 const char g_fragment_shader[] = R"(
-#version 150 core
+#if GL_ES && __VERSION__ >= 300 || !GL_ES && __VERSION__ >= 130
+#define varying in
+#endif
 
-in vec2 frag_tex_coord;
-out vec4 color;
+varying mediump vec2 frag_tex_coord;
+
+#if GL_ES && __VERSION__ >= 300
+out mediump vec4 color;
+#else
+#define color gl_FragColor
+#endif
 
 uniform sampler2D color_texture;
 
 void main() {
-    color = texture(color_texture, frag_tex_coord);
+    color = texture2D(color_texture, frag_tex_coord);
 }
 )";
 

src/video_core/renderer_opengl/renderer_opengl.cpp

@@ -34,12 +34,12 @@ struct ScreenRectVertex {
  * The projection part of the matrix is trivial, hence these operations are represented
  * by a 3x2 matrix.
  */
-static std::array<GLfloat, 3*2> MakeOrthographicMatrix(const float width, const float height) {
-    std::array<GLfloat, 3*2> matrix;
+static std::array<GLfloat, 3*3> MakeOrthographicMatrix(const float width, const float height) {
+    std::array<GLfloat, 3*3> matrix;
 
-    matrix[0] = 2.f / width; matrix[2] = 0.f;           matrix[4] = -1.f;
-    matrix[1] = 0.f;         matrix[3] = -2.f / height; matrix[5] = 1.f;
-    // Last matrix row is implicitly assumed to be [0, 0, 1].
+    matrix[0] = 2.f / width; matrix[3] = 0.f;           matrix[6] = -1.f;
+    matrix[1] = 0.f;         matrix[4] = -2.f / height; matrix[7] = 1.f;
+    matrix[2] = 0.f;         matrix[5] = 0.f;           matrix[8] = 1.f;
 
     return matrix;
 }
@@ -131,11 +131,38 @@ void RendererOpenGL::LoadFBToActiveGLTexture(const GPU::Regs::FramebufferConfig&
  * Initializes the OpenGL state and creates persistent objects.
  */
 void RendererOpenGL::InitOpenGLObjects() {
+    std::string glsl_header;
+
+    // Select the right GLSL version for our context
+    int version = epoxy_gl_version();
+    if (epoxy_is_desktop_gl()) {
+        if (version == 20)
+            glsl_header = "#version 110\n";
+        else if (version == 21)
+            glsl_header = "#version 120\n";
+        else if (version == 30)
+            glsl_header = "#version 130\n";
+        else if (version == 31)
+            glsl_header = "#version 140\n";
+        else if (version == 32)
+            glsl_header = "#version 150\n";
+        else
+            glsl_header = "#version " + std::to_string(version * 10) + "\n";
+
+        // Desktop OpenGL doesn’t support precision qualifiers.
+        glsl_header += "#define mediump\n";
+    } else {
+        if (version == 20)
+            glsl_header = "#version 100\n";
+        else
+            glsl_header = "#version " + std::to_string(version * 10) + " es\n";
+    }
+
     glClearColor(1.0f, 1.0f, 1.0f, 0.0f);
     glDisable(GL_DEPTH_TEST);
 
     // Link shaders and get variable locations
-    program_id = ShaderUtil::LoadShaders(GLShaders::g_vertex_shader, GLShaders::g_fragment_shader);
+    program_id = ShaderUtil::LoadShaders(glsl_header.c_str(), GLShaders::g_vertex_shader, GLShaders::g_fragment_shader);
     uniform_modelview_matrix = glGetUniformLocation(program_id, "modelview_matrix");
     uniform_color_texture = glGetUniformLocation(program_id, "color_texture");
     attrib_position = glGetAttribLocation(program_id, "vert_position");
@@ -201,8 +228,8 @@ void RendererOpenGL::DrawScreens() {
     glUseProgram(program_id);
 
     // Set projection matrix
-    std::array<GLfloat, 3*2> ortho_matrix = MakeOrthographicMatrix((float)resolution_width, (float)resolution_height);
-    glUniformMatrix3x2fv(uniform_modelview_matrix, 1, GL_FALSE, ortho_matrix.data());
+    std::array<GLfloat, 3*3> ortho_matrix = MakeOrthographicMatrix((float)resolution_width, (float)resolution_height);
+    glUniformMatrix3fv(uniform_modelview_matrix, 1, GL_FALSE, ortho_matrix.data());
 
     // Bind texture in Texture Unit 0
     glActiveTexture(GL_TEXTURE0);