Documentation: Replace the bgl API in the gpu module exemples

doc/python_api/examples/gpu.8.py

@@ -7,11 +7,10 @@ If it already exists, it will override the existing one.
 
 Currently almost all of the execution time is spent in the last line.
 In the future this will hopefully be solved by implementing the Python buffer protocol
-for :class:`bgl.Buffer` and :class:`bpy.types.Image.pixels` (aka ``bpy_prop_array``).
+for :class:`gpu.types.Buffer` and :class:`bpy.types.Image.pixels` (aka ``bpy_prop_array``).
 """
 import bpy
 import gpu
-import bgl
 import random
 from mathutils import Matrix
 from gpu_extras.presets import draw_circle_2d
@@ -25,8 +24,8 @@ RING_AMOUNT = 10
 offscreen = gpu.types.GPUOffScreen(WIDTH, HEIGHT)
 
 with offscreen.bind():
-    bgl.glClearColor(0.0, 0.0, 0.0, 0.0)
-    bgl.glClear(bgl.GL_COLOR_BUFFER_BIT)
+    fb = gpu.state.active_framebuffer_get()
+    fb.clear(color=(0.0, 0.0, 0.0, 0.0))
     with gpu.matrix.push_pop():
         # reset matrices -> use normalized device coordinates [-1, 1]
         gpu.matrix.load_matrix(Matrix.Identity(4))
@@ -37,9 +36,7 @@ with offscreen.bind():
                 (random.uniform(-1, 1), random.uniform(-1, 1)),
                 (1, 1, 1, 1), random.uniform(0.1, 1), 20)
 
-    buffer = bgl.Buffer(bgl.GL_BYTE, WIDTH * HEIGHT * 4)
-    bgl.glReadBuffer(bgl.GL_BACK)
-    bgl.glReadPixels(0, 0, WIDTH, HEIGHT, bgl.GL_RGBA, bgl.GL_UNSIGNED_BYTE, buffer)
+    buffer = fb.read_color(0, 0, WIDTH, HEIGHT, 4, 0, 'UBYTE')
 
 offscreen.free()
 
@@ -48,4 +45,6 @@ if not IMAGE_NAME in bpy.data.images:
     bpy.data.images.new(IMAGE_NAME, WIDTH, HEIGHT)
 image = bpy.data.images[IMAGE_NAME]
 image.scale(WIDTH, HEIGHT)
+
+buffer.dimensions = WIDTH * HEIGHT * 4
 image.pixels = [v / 255 for v in buffer]