Attract: draw using the GPU module

The drawing is rather primitive, but it works.

blender_cloud/attract/draw.py

@@ -18,9 +18,12 @@
 
 # <pep8 compliant>
 
-import bpy
 import logging
-import collections
+import typing
+
+import bpy
+import bgl
+import gpu
 
 log = logging.getLogger(__name__)
 
@@ -34,10 +37,74 @@ strip_status_colour = {
     'todo': (1.0, 0.5019607843137255, 0.5019607843137255)
 }
 
-CONFLICT_COLOUR = (0.576, 0.118, 0.035)  # RGB tuple
+CONFLICT_COLOUR = (0.576, 0.118, 0.035, 1.0)  # RGBA tuple
+
+gpu_vertex_shader = '''
+uniform mat4 ModelViewProjectionMatrix;
+
+layout (location = 0) in vec2 pos;
+layout (location = 1) in vec4 color;
+
+out vec4 lineColor; // output to the fragment shader
+
+void main()
+{
+    gl_Position = ModelViewProjectionMatrix * vec4(pos.x, pos.y, 0.0, 1.0);
+    lineColor = color;
+}
+'''
+
+gpu_fragment_shader = '''
+out vec4 fragColor;
+in vec4 lineColor;
+
+void main()
+{
+    fragColor = lineColor;
+}
+'''
+
+Float2 = typing.Tuple[float, float]
+Float3 = typing.Tuple[float, float, float]
+Float4 = typing.Tuple[float, float, float, float]
 
 
-def get_strip_rectf(strip):
+class AttractLineDrawer:
+
+    def __init__(self):
+        self._format = gpu.types.GPUVertFormat()
+        self._pos_id = self._format.attr_add(
+            id="pos",
+            comp_type="F32",
+            len=2,
+            fetch_mode="FLOAT")
+        self._color_id = self._format.attr_add(
+            id="color",
+            comp_type="F32",
+            len=4,
+            fetch_mode="FLOAT")
+
+        self.shader = gpu.types.GPUShader(gpu_vertex_shader, gpu_fragment_shader)
+
+    def draw(self,
+             coords: typing.List[Float2],
+             colors: typing.List[Float4]):
+        if not coords:
+            return
+
+        bgl.glEnable(bgl.GL_BLEND)
+        bgl.glLineWidth(2.0)
+
+        vbo = gpu.types.GPUVertBuf(len=len(coords), format=self._format)
+        vbo.attr_fill(id=self._pos_id, data=coords)
+        vbo.attr_fill(id=self._color_id, data=colors)
+
+        batch = gpu.types.GPUBatch(type="LINES", buf=vbo)
+        batch.program_set(self.shader)
+        batch.draw()
+
+
+def get_strip_rectf(strip) -> Float4:
     # Get x and y in terms of the grid's frames and channels
     x1 = strip.frame_final_start
     x2 = strip.frame_final_end
@@ -47,59 +114,56 @@ def get_strip_rectf(strip):
     return x1, y1, x2, y2
 
 
-def draw_underline_in_strip(strip_coords, pixel_size_x, color):
+def underline_in_strip(strip_coords: Float4,
-    from bgl import glColor4f, glRectf, glEnable, glDisable, GL_BLEND
+                       pixel_size_x: float,
-    import bgl
+                       color: Float4,
-
+                       out_coords: typing.List[Float2],
-    context = bpy.context
+                       out_colors: typing.List[Float4]):
-
     # Strip coords
     s_x1, s_y1, s_x2, s_y2 = strip_coords
 
     # be careful not to draw over the current frame line
-    cf_x = context.scene.frame_current_final
+    cf_x = bpy.context.scene.frame_current_final
 
-    bgl.glPushAttrib(bgl.GL_COLOR_BUFFER_BIT | bgl.GL_LINE_BIT)
+    # TODO(Sybren): figure out how to pass one colour per line,
+    # instead of one colour per vertex.
+    out_coords.append((s_x1, s_y1))
+    out_colors.append(color)
 
-    glColor4f(*color)
-    glEnable(GL_BLEND)
-    bgl.glLineWidth(2)
-    bgl.glBegin(bgl.GL_LINES)
-
-    bgl.glVertex2f(s_x1, s_y1)
     if s_x1 < cf_x < s_x2:
-        # Bad luck, the line passes our strip
+        # Bad luck, the line passes our strip, so draw two lines.
-        bgl.glVertex2f(cf_x - pixel_size_x, s_y1)
+        out_coords.append((cf_x - pixel_size_x, s_y1))
-        bgl.glVertex2f(cf_x + pixel_size_x, s_y1)
+        out_colors.append(color)
-    bgl.glVertex2f(s_x2, s_y1)
 
-    bgl.glEnd()
+        out_coords.append((cf_x + pixel_size_x, s_y1))
-    bgl.glPopAttrib()
+        out_colors.append(color)
+
+    out_coords.append((s_x2, s_y1))
+    out_colors.append(color)
 
 
-def draw_strip_conflict(strip_coords, pixel_size_x):
+def strip_conflict(strip_coords: Float4,
+                   out_coords: typing.List[Float2],
+                   out_colors: typing.List[Float4]):
     """Draws conflicting states between strips."""
 
-    import bgl
-
     s_x1, s_y1, s_x2, s_y2 = strip_coords
-    bgl.glPushAttrib(bgl.GL_COLOR_BUFFER_BIT | bgl.GL_LINE_BIT)
 
-    # Always draw the full rectangle, the conflict should be resolved and thus stand out.
+    # TODO(Sybren): draw a rectangle instead of a line.
-    bgl.glColor3f(*CONFLICT_COLOUR)
+    out_coords.append((s_x1, s_y2))
-    bgl.glLineWidth(2)
+    out_colors.append(CONFLICT_COLOUR)
 
-    bgl.glBegin(bgl.GL_LINE_LOOP)
+    out_coords.append((s_x2, s_y1))
-    bgl.glVertex2f(s_x1, s_y1)
+    out_colors.append(CONFLICT_COLOUR)
-    bgl.glVertex2f(s_x2, s_y1)
-    bgl.glVertex2f(s_x2, s_y2)
-    bgl.glVertex2f(s_x1, s_y2)
-    bgl.glEnd()
 
-    bgl.glPopAttrib()
+    out_coords.append((s_x2, s_y2))
+    out_colors.append(CONFLICT_COLOUR)
+
+    out_coords.append((s_x1, s_y1))
+    out_colors.append(CONFLICT_COLOUR)
 
 
-def draw_callback_px():
+def draw_callback_px(line_drawer: AttractLineDrawer):
     context = bpy.context
 
     if not context.scene.sequence_editor:
@@ -115,6 +179,10 @@ def draw_callback_px():
 
     strips = shown_strips(context)
 
+    coords: typing.List[Float2] = []
+    colors: typing.List[Float4] = []
+
+    # Collect all the lines (vertex coords + vertex colours) to draw.
     for strip in strips:
         if not strip.atc_object_id:
             continue
@@ -136,9 +204,11 @@ def draw_callback_px():
 
         alpha = 1.0 if strip.atc_is_synced else 0.5
 
-        draw_underline_in_strip(strip_coords, pixel_size_x, color + (alpha,))
+        underline_in_strip(strip_coords, pixel_size_x, color + (alpha,), coords, colors)
         if strip.atc_is_synced and strip.atc_object_id_conflict:
-            draw_strip_conflict(strip_coords, pixel_size_x)
+            strip_conflict(strip_coords, coords, colors)
+
+    line_drawer.draw(coords, colors)
 
 
 def tag_redraw_all_sequencer_editors():
@@ -162,8 +232,9 @@ def callback_enable():
     if cb_handle:
         return
 
+    line_drawer = AttractLineDrawer()
     cb_handle[:] = bpy.types.SpaceSequenceEditor.draw_handler_add(
-        draw_callback_px, (), 'WINDOW', 'POST_VIEW'),
+        draw_callback_px, (line_drawer,), 'WINDOW', 'POST_VIEW'),
 
     tag_redraw_all_sequencer_editors()