1 files changed, 123 insertions, 0 deletions
diff --git a/src/render/canvas.cpp b/src/render/canvas.cpp
new file mode 100644
index 0000000..494b0fa
--- /dev/null
+++ b/src/render/canvas.cpp
@@ -0,0 +1,123 @@
+#include "utils/macros.h"
+#include "canvas.h" 
+#include "window.h"
+
+namespace jin
+{
+namespace render 
+{
+    Canvas::Canvas() :Drawable()
+    {
+    }
+
+    Canvas::~Canvas()
+    {
+    }
+
+    // no canvas has binded 
+    shared GLint Canvas::cur = -1; 
+
+    bool Canvas::init(int w, int h)
+    {
+        Drawable::init(w, h);
+        Drawable::setVertices(
+            new float [DRAWABLE_V_SIZE] {
+                0, 0,
+                0, (float)h,
+                (float)w, (float)h,
+                (float)w, 0,
+            },
+            new float [DRAWABLE_V_SIZE] {
+                0, 1,
+                0, 0,
+                1, 0,
+                1, 1
+            }
+        );
+
+        GLint current_fbo;
+        glGetIntegerv(GL_DRAW_FRAMEBUFFER_BINDING, &current_fbo);
+
+        // generate a new render buffer object 
+        glGenFramebuffers(1, &fbo);
+        glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+
+        // generate texture save target 
+        glGenTextures(1, &texture);
+        glBindTexture(GL_TEXTURE_2D, texture);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
+        glBindTexture(GL_TEXTURE_2D, 0);
+        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture, 0);
+
+        GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
+        
+        // unbind framebuffer
+        glBindFramebuffer(GL_FRAMEBUFFER, current_fbo);
+        
+        if (status != GL_FRAMEBUFFER_COMPLETE_EXT)
+            return false;
+        return true; 
+    }
+
+    bool Canvas::hasbind(GLint fbo)
+    {
+        return cur == fbo; 
+    }
+
+    /**
+    * bind to canvas 
+    */
+    void Canvas::bind()
+    {
+        if (hasbind(fbo)) return;
+
+        cur = fbo;
+
+        glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+
+        glMatrixMode(GL_PROJECTION);
+        glPushMatrix();
+        glLoadIdentity();
+
+        glViewport(0, 0, width, height);
+        glOrtho(0, width, height, 0, -1, 1);
+
+        // Switch back to modelview matrix
+        glMatrixMode(GL_MODELVIEW);
+        glPushMatrix();
+        glLoadIdentity();
+    }
+
+    /**
+    * bind to default screen render buffer. 
+    */
+    shared void Canvas::unbind()
+    {
+        if (hasbind(0)) return;
+        
+        cur = 0;
+
+        glBindFramebuffer(GL_FRAMEBUFFER, 0);
+        Window* wnd = Window::get();
+        int ww = wnd->getW(),
+            wh = wnd->getH();
+
+        glViewport(0, 0, ww, wh);
+
+        // load back to normal 
+        glMatrixMode(GL_PROJECTION);
+        glPushMatrix();
+        glLoadIdentity();
+        
+        // set viewport matrix 
+        glOrtho(0, ww, wh, 0, -1, 1);
+
+        //  switch to model matrix  
+        glMatrixMode(GL_MODELVIEW);
+        glPushMatrix();
+        glLoadIdentity();
+    }
+}
+}
+\ No newline at end of file