infra: added opengl_es extra option for explicit selection

usages:
meson setup build -Dengines="gl"  //opengl
meson setup build -Dengines="gl" -Dextra="opengl_es"  //opengl es

examples/meson.build

@@ -4,7 +4,7 @@ if lib_type == 'static'
     examples_compiler_flags += ['-DTVG_STATIC']
 endif
 
-if target_opengles
+if gl_variant == 'OpenGL ES'
     examples_compiler_flags += '-DTHORVG_GL_TARGET_GLES=1'
 endif
 

meson.build

@@ -132,6 +132,18 @@ if lottie_expressions
     config_h.set10('THORVG_LOTTIE_EXPRESSIONS_SUPPORT', true)
 endif
 
+gl_variant = ''
+
+if gl_engine
+    if get_option('extra').contains('opengl_es')
+        gl_variant = 'OpenGL ES'
+    else
+        gl_variant = 'OpenGL'
+    endif
+else
+    gl_variant = 'None'
+endif
+
 #Miscellaneous
 config_h.set10('WIN32_LEAN_AND_MEAN', true)
 
@@ -142,9 +154,6 @@ 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')
@@ -183,6 +192,7 @@ Summary:
     Tool (Svg2Png):             @20@
     Tool (Lottie2Gif):          @21@
     Extra (Lottie Expressions): @22@
+    Extra (OpenGL Variant):     @23@
 
 '''.format(
         meson.project_version(),
@@ -207,7 +217,8 @@ Summary:
         get_option('examples'),
         svg2png,
         lottie2gif,
-        lottie_expressions
+        lottie_expressions,
+        gl_variant
     )
 
 message(summary)

meson_options.txt

@@ -65,6 +65,6 @@ option('file',
 
 option('extra',
    type: 'array',
-   choices: ['', 'lottie_expressions'],
+   choices: ['', 'opengl_es', 'lottie_expressions'],
    value: ['lottie_expressions'],
-   description: '"Enable support for exceptionally advanced features')
+   description: '"Enable support for extra options')

src/renderer/gl_engine/meson.build

@@ -24,39 +24,19 @@ source_file = [
    'tvgGlTessellator.h',
 ]
 
-if host_machine.system() == 'darwin'
-    gl_dep = declare_dependency(link_args: ['-framework', 'OpenGL'])
-    compiler_flags += ['-Wno-deprecated']     #for deprecated opengl
-elif cc.get_id() == 'emscripten'
-    target_opengles = true
-    gl_dep = dependency('GLESv3', required: false)
-else
-    #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
+#force to use gles
+if cc.get_id() == 'emscripten'
+    gl_variant = 'OpenGL ES'
 endif
 
-if target_opengles
-    gl_target_profile = '-DTHORVG_GL_TARGET_GLES=1'
+if gl_variant == 'OpenGL ES'
+    gl_variant_profile = '-DTHORVG_GL_TARGET_GLES=1'
 else
-    gl_target_profile = '-DTHORVG_GL_TARGET_GL=1'
+    gl_variant_profile = '-DTHORVG_GL_TARGET_GL=1'
 endif
 
 engine_dep += [declare_dependency(
-    compile_args        : gl_target_profile,
+    compile_args        : gl_variant_profile,
     include_directories : include_directories('.'),
     sources             : source_file,
 )]