fix mixer rect, textures popup, parallel abr import

src/canvas.cpp

@@ -444,7 +444,7 @@ std::vector<Canvas::StrokeFrame> Canvas::stroke_draw_compute(Stroke& stroke) con
             B[j].uvs2 = p / mixer_sz;
         }
         
-        f.m_mixer_rect = { mixer_bb_min, mixer_bb_max - mixer_bb_min };
+        f.m_mixer_rect = { glm::floor(mixer_bb_min), glm::ceil(mixer_bb_max - mixer_bb_min) };
         f.col = glm::vec4(s.col, 1);
         f.pressure = s.flow;
         f.shapes = stroke_draw_project(B);