integrate Kovak's ScissorPush/Pop instructions, documentation needed

kivy/factory_registers.py

@@ -65,6 +65,8 @@ r('StencilPush', module='kivy.graphics.stencil_instructions')
 r('StencilPop', module='kivy.graphics.stencil_instructions')
 r('StencilUse', module='kivy.graphics.stencil_instructions')
 r('StencilUnUse', module='kivy.graphics.stencil_instructions')
+r('ScissorPush', module='kivy.graphics.scissor_instructions')
+r('ScissorPop', module='kivy.graphics.scissor_instructions')
 r('Triangle', module='kivy.graphics.vertex_instructions')
 r('Quad', module='kivy.graphics.vertex_instructions')
 r('Rectangle', module='kivy.graphics.vertex_instructions')

kivy/graphics/scissor_instructions.pyx

@@ -0,0 +1,158 @@
+include "config.pxi"
+include "opcodes.pxi"
+
+from kivy.graphics.c_opengl cimport *
+IF USE_OPENGL_DEBUG == 1:
+    from kivy.graphics.c_opengl_debug cimport *
+from kivy.graphics.instructions cimport Instruction
+
+cdef class Rect:
+    cdef int _x
+    cdef int _y
+    cdef int _width
+    cdef int _height
+
+    def __init__(self, int x, int y, int width, int height):
+        self._x = x
+        self._y = y
+        self._width = width
+        self._height = height
+
+    def intersect(self, Rect other):
+        max_x = min(self._x + self._width, other._x + other._width)
+        x = max(self._x, other._x)
+        width = max(0, max_x - x)
+        max_y = min(self._y + self._height, other._y + other._height)
+        y = max(self._y, other._y)
+        height = max(0, max_y - y)
+        self._x = x
+        self._width = width
+        self._y = y
+        self._height = height
+
+
+cdef class ScissorStack:
+    cdef list _stack
+
+    def __init__(self):
+        self._stack = []
+
+    property empty:
+        def __get__(self):
+            return True if len(self._stack) is 0 else False
+
+    property back:
+        def __get__(self):
+            return self._stack[-1]
+
+    def push(self, element):
+        self._stack.append(element)
+
+    def pop(self):
+        return self._stack.pop()
+
+
+scissor_stack = ScissorStack()
+
+
+cdef class ScissorPush(Instruction):
+    cdef int _x
+    cdef int _y
+    cdef int _width
+    cdef int _height
+    cdef bint _on
+    cdef Rect _rect
+
+    property x:
+        def __get__(self):
+            return self._x
+        def __set__(self, value):
+            self._x = value
+            self._rect = Rect(self._x, self._y, self._width, self._height)
+            self.flag_update()
+
+    property y:
+        def __get__(self):
+            return self._y
+        def __set__(self, value):
+            self._y = value
+            self._rect = Rect(self._x, self._y, self._width, self._height)
+            self.flag_update()
+
+    property width:
+        def __get__(self):
+            return self._width
+        def __set__(self, value):
+            self._width = value
+            self._rect = Rect(self._y, self._y, self._width, self._height)
+            self.flag_update()
+
+    property height:
+        def __get__(self):
+            return self._height
+        def __set__(self, value):
+            self._height = value
+            self._rect = Rect(self._y, self._y, self._width, self._height)
+            self.flag_update()
+
+    property pos:
+        def __get__(self):
+            return self._x, self._y
+        def __set__(self, value):
+            self._x, self._y = value
+            self._rect = Rect(self._x, self._y, self._width, self._height)
+            self.flag_update()
+
+    property size:
+        def __get__(self):
+            return self._width, self._height
+        def __set__(self, value):
+            self._width, self._height = value
+            self._rect = Rect(self._x, self._y, self._width, self._height)
+            self.flag_update()
+
+    def __init__(self, **kwargs):
+        super(ScissorPush, self).__init__(**kwargs)
+        pos = kwargs.get('pos', (kwargs.get('x', 0), kwargs.get('y', 0)))
+        self._x, self._y = kwargs.get(
+            'pos', (
+                kwargs.get('x', 0),
+                kwargs.get('y', 0)
+                )
+            )
+        self._width, self._height = kwargs.get(
+            'size', (
+                kwargs.get('width', 100),
+                kwargs.get('height', 100)
+                )
+            )
+        self._rect = Rect(self._x, self._y, self._width, self._height)
+
+    cdef void apply(self):
+        cdef Rect rect = self._rect
+        cdef Rect new_scissor_rect
+        cdef Rect back
+        if scissor_stack.empty:
+            scissor_stack.push(rect)
+            glEnable(GL_SCISSOR_TEST)
+            glScissor(self._x, self._y, self._width, self._height)
+        else:
+            new_scissor_rect = Rect(rect._x, rect._y, 
+                rect._width, rect._height)
+            back = scissor_stack.back
+            new_scissor_rect.intersect(back)
+            scissor_stack.push(new_scissor_rect)
+            glScissor(new_scissor_rect._x, new_scissor_rect._y, 
+                new_scissor_rect._width, new_scissor_rect._height)
+
+cdef class ScissorPop(Instruction):
+
+    cdef void apply(self):
+        scissor_stack.pop()
+        cdef Rect new_scissor_rect
+        if scissor_stack.empty:
+            glDisable(GL_SCISSOR_TEST)
+        else:
+            new_scissor_rect = scissor_stack.back
+            glScissor(new_scissor_rect._x, new_scissor_rect._y, 
+                new_scissor_rect._width, new_scissor_rect._height)

setup.py

@@ -425,6 +425,8 @@ graphics_dependencies = {
     'stencil_instructions.pxd': ['instructions.pxd'],
     'stencil_instructions.pyx': [
         'config.pxi', 'opcodes.pxi', 'c_opengl.pxd', 'c_opengl_debug.pxd'],
+    'scissor_instructions.pyx': [
+        'config.pxi', 'opcodes.pxi', 'c_opengl.pxd', 'c_opengl_debug.pxd'],
     'texture.pxd': ['c_opengl.pxd'],
     'texture.pyx': [
         'config.pxi', 'common.pxi', 'opengl_utils_def.pxi', 'context.pxd',
@@ -457,6 +459,7 @@ sources = {
     'graphics/opengl_utils.pyx': merge(base_flags, gl_flags),
     'graphics/shader.pyx': merge(base_flags, gl_flags),
     'graphics/stencil_instructions.pyx': merge(base_flags, gl_flags),
+    'graphics/scissor_instructions.pyx': merge(base_flags, gl_flags),
     'graphics/texture.pyx': merge(base_flags, gl_flags),
     'graphics/transformation.pyx': merge(base_flags, gl_flags),
     'graphics/vbo.pyx': merge(base_flags, gl_flags),