Fixes #12 alpha issue: only enable blend for fbo->screen drawing

RNGL/GLCanvas.m

@@ -286,6 +286,8 @@ RCT_NOT_IMPLEMENTED(-init)
 
 - (void)drawRect:(CGRect)rect
 {
+  self.layer.opaque = _opaque;
+  [self syncEventsThrough];
   
   if (!_preloadingDone) {
     glClearColor(0.0, 0.0, 0.0, 0.0);
@@ -309,9 +311,6 @@ RCT_NOT_IMPLEMENTED(-init)
 {
   if (!_renderData) return;
   
-  self.layer.opaque = _opaque;
-  [self syncEventsThrough];
-  
   CGFloat scale = RCTScreenScale();
   
   @autoreleasepool {
@@ -355,12 +354,19 @@ RCT_NOT_IMPLEMENTED(-init)
       glDrawArrays(GL_TRIANGLES, 0, 6);
     };
     
+    // DRAWING THE SCENE
+    
     glGetIntegerv(GL_FRAMEBUFFER_BINDING, &defaultFBO);
     
+    glDisable(GL_BLEND);
+    
     [self syncContentTextures];
     
     recDraw(_renderData);
     
+    glEnable(GL_BLEND);
+    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+    
     glBindFramebuffer(GL_FRAMEBUFFER, defaultFBO);
   }
 }

RNGL/GLShader.m

@@ -346,9 +346,6 @@ GLuint compileShader (NSString* shaderName, NSString* shaderString, GLenum shade
 {
   if (![self ensureContext]) return;
 
-  glEnable(GL_BLEND);
-  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
-
   GLuint vertex = compileShader(_name, _vert, GL_VERTEX_SHADER);
   if (vertex == -1) return;