implement multithreaded rendering with context switch, gl state save/restore, add progress bar ui node, implement stencil texture for brush, implement multithreaded canvas load/save/export pano. Missing multithread in windows.

engine/util.h

@@ -111,4 +111,55 @@ public:
     }
 };
 
+struct gl_state
+{
+    GLboolean blend;
+    GLboolean depth_test;
+    GLboolean scissor_test;
+    GLint vp[4];
+    GLfloat cc[4];
+    GLint tex[10];
+    GLint cube;
+    GLint sampler[10];
+    GLint program;
+    GLint fb;
+    GLint active_tex;
+    void save()
+    {
+        blend = glIsEnabled(GL_BLEND);
+        depth_test = glIsEnabled(GL_DEPTH_TEST);
+        scissor_test = glIsEnabled(GL_SCISSOR_TEST);
+        glGetIntegerv(GL_VIEWPORT, vp);
+        glGetFloatv(GL_COLOR_CLEAR_VALUE, cc);
+        glGetIntegerv(GL_CURRENT_PROGRAM, &program);
+        glGetIntegerv(GL_FRAMEBUFFER_BINDING, &fb);
+        glGetIntegerv(GL_ACTIVE_TEXTURE, &active_tex);
+        glGetIntegerv(GL_TEXTURE_BINDING_CUBE_MAP, &cube);
+        for (int i = 0; i < 10; ++i)
+        {
+            glActiveTexture(GL_TEXTURE0 + i);
+            glGetIntegerv(GL_TEXTURE_BINDING_2D, tex + i);
+            glGetIntegerv(GL_SAMPLER_BINDING, sampler + i);
+        }
+    }
+    void restore()
+    {
+        blend ? glEnable(GL_BLEND) : glDisable(GL_BLEND);
+        depth_test ? glEnable(GL_DEPTH_TEST) : glDisable(GL_DEPTH_TEST);
+        scissor_test ? glEnable(GL_SCISSOR_TEST) : glDisable(GL_SCISSOR_TEST);
+        glViewport(vp[0], vp[1], vp[2], vp[3]);
+        glClearColor(cc[0], cc[1], cc[2], cc[3]);
+        glBindFramebuffer(GL_FRAMEBUFFER, fb);
+        glUseProgram(program);
+        for (int i = 0; i < 10; ++i)
+        {
+            glActiveTexture(GL_TEXTURE0 + i);
+            glBindTexture(GL_TEXTURE_2D, tex[i]);
+            glBindSampler(i, sampler[i]);
+        }
+        glActiveTexture(active_tex);
+        glBindTexture(GL_TEXTURE_BINDING_CUBE_MAP, cube);
+    }
+};
+
 NS_END