gl_engine: revise the gl portability

- guarantee minimum gl version requirement
- removed glesv2 dependency
- corrected gl ver dependency

issue: https://github.com/thorvg/thorvg/issues/2282

README.md

@@ -494,7 +494,7 @@ meson setup builddir -Dbindings="capi"
 ## Dependencies
 ThorVG offers versatile support for image loading, accommodating both static and external loaders. This flexibility ensures that, even in environments without external libraries, users can still leverage static loaders as a reliable alternative. At its foundation, the ThorVG core library is engineered to function autonomously, free from external dependencies. However, it is important to note that ThorVG also encompasses a range of optional feature extensions, each with its specific set of dependencies. The dependencies associated with these selective features are outlined as follows:
 
-* GL engine: [GLESv2/GLESv3](https://www.khronos.org/opengles/)
+* GL engine: [OpenGL v3.3](https://www.khronos.org/opengl/) or [GLES v3.0](https://www.khronos.org/opengles/)
 * WG engine: [webgpu-native](https://github.com/gfx-rs/wgpu-native)
 * External PNG support: [libpng](https://github.com/glennrp/libpng)
 * External JPG support: [turbojpeg](https://github.com/libjpeg-turbo/libjpeg-turbo)

examples/Example.h

@@ -317,19 +317,16 @@ struct GlWindow : Window
 
     GlWindow(Example* example, uint32_t width, uint32_t height) : Window(tvg::CanvasEngine::Gl, example, width, height)
     {
+#ifdef THORVG_GL_TARGET_GLES
+        SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);
         SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
         SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
-        SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);
+#else
-        window = SDL_CreateWindow("ThorVG Example (OpenGLES)", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, width, height, SDL_WINDOW_OPENGL | SDL_WINDOW_HIDDEN | SDL_WINDOW_RESIZABLE);
+        SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
-
-        if (window == nullptr) {
-            // try create OpenGLES context failed, create OpenGL context instead
         SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
         SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
-            SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
+#endif
-            window = SDL_CreateWindow("ThorVG Example (OpenGL)", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, width, height, SDL_WINDOW_OPENGL | SDL_WINDOW_HIDDEN | SDL_WINDOW_RESIZABLE);
+        window = SDL_CreateWindow("ThorVG Example (OpenGL/ES)", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, width, height, SDL_WINDOW_OPENGL | SDL_WINDOW_HIDDEN | SDL_WINDOW_RESIZABLE);
-        }
-
         context = SDL_GL_CreateContext(window);
     }
 

examples/meson.build

@@ -2,6 +2,10 @@ if (lib_type == 'static')
     compiler_flags += ['-DTVG_STATIC']
 endif
 
+if target_opengles
+    compiler_flags += '-DTHORVG_GL_TARGET_GLES=1'
+endif
+
 examples_dep = [dependency('sdl2')]
 
 if (get_option('engines').contains('wg_beta'))

meson.build

@@ -144,6 +144,9 @@ configure_file(
 
 headers = [include_directories('inc'), include_directories('.')]
 
+#OpenGL profile: OpenGLES(true) or OpenGL(false), confirmed by gl_engine
+target_opengles = false
+
 subdir('inc')
 subdir('src')
 subdir('tools')

src/renderer/gl_engine/meson.build

@@ -21,42 +21,36 @@ source_file = [
    'tvgGlTessellator.h',
 ]
 
-#find a gl library with fallbacks
+if host_machine.system() == 'darwin'
-gles_dep = meson.get_compiler('cpp').find_library('GLESv3', required: false)
+    gl_dep = declare_dependency(link_args: ['-framework', 'OpenGL'])
-
-if not gles_dep.found()
-  gles_dep = dependency('GLESv3', required: false)
-endif
-
-if not gles_dep.found()
-  gles_dep = meson.get_compiler('cpp').find_library('GLESv2', required: false)
-endif
-
-if not gles_dep.found()
-  gles_dep = dependency('GLESv2', required: false)
-endif
-
-link_opengl = false
-
-if not gles_dep.found()
-  gles_dep = dependency('GL')
-  link_opengl = true
-endif
-
-if not gles_dep.found()
-  gles_dep = meson.get_compiler('cpp').find_library('GL')
-  link_opengl = true
-endif
-
-if link_opengl
-    gl_target_define = '-DTHORVG_GL_TARGET_GL=1'
 else
-    gl_target_define = '-DTHORVG_GL_TARGET_GLES=1'
+    #find a opengl library with fallbacks
+    gl_dep = dependency('GL', required: false)
+
+    if not gl_dep.found()
+        gl_dep = meson.get_compiler('cpp').find_library('GL', required: false)
+    endif
+
+    if not gl_dep.found()
+        gl_dep = dependency('GLESv3', required: false)
+        target_opengles = true
+    endif
+
+    if not gl_dep.found()
+        gl_dep = meson.get_compiler('cpp').find_library('GLESv3')
+        target_opengles = true
+    endif
+endif
+
+if target_opengles
+    gl_target_profile = '-DTHORVG_GL_TARGET_GLES=1'
+else
+    gl_target_profile = '-DTHORVG_GL_TARGET_GL=1'
 endif
 
 engine_dep += [declare_dependency(
-    compile_args        : gl_target_define,
+    compile_args        : gl_target_profile,
-    dependencies        : gles_dep,
+    dependencies        : gl_dep,
     include_directories : include_directories('.'),
     sources             : source_file,
 )]

src/renderer/gl_engine/tvgGlCommon.h

@@ -26,12 +26,17 @@
 #include <assert.h>
 #if defined (THORVG_GL_TARGET_GLES)
     #include <GLES3/gl3.h>
-#elif defined (THORVG_GL_TARGET_GL)
+    #define TVG_REQUIRE_GL_MAJOR_VER 3
+    #define TVG_REQUIRE_GL_MINOR_VER 0
+#else
     #if defined(__APPLE__) || defined(__MACH__)
         #include <OpenGL/gl3.h>
     #else
-        #include <GL/gl3.h>
+        #define GL_GLEXT_PROTOTYPES 1
+        #include <GL/gl.h>
     #endif
+    #define TVG_REQUIRE_GL_MAJOR_VER 3
+    #define TVG_REQUIRE_GL_MINOR_VER 3
 #endif
 #include "tvgCommon.h"
 #include "tvgRender.h"

src/renderer/gl_engine/tvgGlRenderer.cpp

@@ -485,7 +485,7 @@ int GlRenderer::init(uint32_t threads)
 {
     if ((initEngineCnt++) > 0) return true;
 
-    //TODO:
+    //TODO: runtime linking?
 
     return true;
 }
@@ -511,13 +511,25 @@ int GlRenderer::term()
 
 GlRenderer* GlRenderer::gen()
 {
+    //TODO: GL minimum version check, should be replaced with the runtime linking in GlRenderer::init()
+    GLint vMajor, vMinor;
+    glGetIntegerv(GL_MAJOR_VERSION, &vMajor);
+    glGetIntegerv(GL_MINOR_VERSION, &vMinor);
+    if (vMajor < TVG_REQUIRE_GL_MAJOR_VER || (vMajor ==  TVG_REQUIRE_GL_MAJOR_VER && vMinor <  TVG_REQUIRE_GL_MINOR_VER)) {
+        TVGERR("GL_ENGINE", "OpenGL/ES version is not statisfied. Current: v%d.%d, Required: v%d.%d", vMajor, vMinor, TVG_REQUIRE_GL_MAJOR_VER, TVG_REQUIRE_GL_MINOR_VER);
+        return nullptr;
+    }
+    TVGLOG("GL_ENGINE", "OpenGL/ES version = v%d.%d", vMajor, vMinor);
+
     return new GlRenderer();
 }
 
+
 GlRenderer::GlRenderer() :mGpuBuffer(new GlStageBuffer), mPrograms(), mComposePool()
 {
 }
 
+
 GlRenderer::~GlRenderer()
 {
     for (uint32_t i = 0; i < mComposePool.count; i++) {

src/renderer/gl_engine/tvgGlShader.cpp

@@ -76,7 +76,7 @@ uint32_t GlShader::complileShader(uint32_t type, char* shaderSrc)
     // but in general All Desktop GPU should use OpenGL version ( #version 330 core )
 #if defined (THORVG_GL_TARGET_GLES)
     shaderPack[0] ="#version 300 es\n";
-#elif defined (THORVG_GL_TARGET_GL)
+#else
     shaderPack[0] ="#version 330 core\n";
 #endif
     shaderPack[1] = "precision highp float;\n precision mediump int;\n";