implement layer bounds optminize function, add history to draw_objects with the right bounds.

src/rtt.cpp

@@ -70,6 +70,19 @@ void RTT::destroy()
 //    h = 0;
 }
 
+void RTT::copy(const RTT & source)
+{
+    glGetIntegerv(GL_DRAW_FRAMEBUFFER_BINDING, &oldDFboID);
+    glGetIntegerv(GL_READ_FRAMEBUFFER_BINDING, &oldRFboID);
+
+    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fboID);
+    glBindFramebuffer(GL_READ_FRAMEBUFFER, source.fboID);
+    glBlitFramebuffer(0, 0, source.w, source.h, 0, 0, w, h, GL_COLOR_BUFFER_BIT, GL_LINEAR);
+
+    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, oldDFboID);
+    glBindFramebuffer(GL_READ_FRAMEBUFFER, oldRFboID);
+}
+
 bool RTT::create(int width, int height, int tex/* = -1*/, GLint internal_format)
 {
     // Destroy any previously created object
@@ -182,6 +195,25 @@ void RTT::clear(glm::vec4 color)
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 }
 
+glm::ivec4 RTT::calc_bounds()
+{
+    auto data = std::unique_ptr<glm::i8vec4[]>(reinterpret_cast<glm::i8vec4*>(readTextureData()));
+    glm::ivec2 bbmin(w, h);
+    glm::ivec2 bbmax(0);
+    for (int y = 0; y < h; y++)
+    {
+        for (int x = 0; x < w; x++)
+        {
+            if (data[x + y * w].a > 0)
+            {
+                bbmin = glm::min(bbmin, { x, y });
+                bbmax = glm::max(bbmax, { x + 1, y + 1 });
+            }
+        }
+    }
+    return { bbmin, bbmax };
+}
+
 uint8_t* RTT::readTextureData(uint8_t* buffer)
 {
     if (!buffer)