Working on music cross fade and settings

src/UiManager.cpp

@@ -327,16 +327,16 @@ namespace ZL {
 		knobMesh.data.PositionData.clear();
 		knobMesh.data.TexCoordData.clear();
 
-		float kw = vertical ? rect.w * 4.0f : rect.w * 0.5f;
-		float kh = vertical ? rect.w * 4.0f : rect.h * 0.5f;
-
-		float cx = rect.x + rect.w * 0.5f;
-		float cy = rect.y + (vertical ? (value * rect.h) : (rect.h * 0.5f));
-
-		float x0 = cx - kw * 0.5f;
-		float y0 = cy - kh * 0.5f;
-		float x1 = cx + kw * 0.5f;
-		float y1 = cy + kh * 0.5f;
+		// Knob is built centered at the middle of the track rect.
+		// draw() applies a per-frame translation so the knob tracks the current value
+		// without needing to rebuild the VBO on every value change.
+		const float kSize = vertical ? rect.w * 2.0f : rect.h;
+		const float cx = rect.x + rect.w * 0.5f;
+		const float cy = rect.y + rect.h * 0.5f;
+		const float x0 = cx - kSize * 0.5f;
+		const float y0 = cy - kSize * 0.5f;
+		const float x1 = cx + kSize * 0.5f;
+		const float y1 = cy + kSize * 0.5f;
 
 		knobMesh.data.PositionData.push_back({ x0, y0, 0 });
 		knobMesh.data.TexCoordData.push_back({ 0, 0 });
@@ -366,8 +366,15 @@ namespace ZL {
 			renderer.DrawVertexRenderStruct(trackMesh);
 		}
 		if (texKnob) {
+			// The knob mesh is built centered at the middle of the track rect.
+			// Translate it so its center lands on the value position along the track.
+			const float offsetX = vertical ? 0.0f : (value - 0.5f) * rect.w;
+			const float offsetY = vertical ? (value - 0.5f) * rect.h : 0.0f;
+			renderer.PushMatrix();
+			renderer.TranslateMatrix({ offsetX, offsetY, 0.0f });
 			glBindTexture(GL_TEXTURE_2D, texKnob->getTexID());
 			renderer.DrawVertexRenderStruct(knobMesh);
+			renderer.PopMatrix();
 		}
 	}
 
@@ -1301,7 +1308,6 @@ namespace ZL {
 		if (fabs(s->value - value) < 1e-6f) return true;
 		s->value = value;
 		s->buildTrackMesh();
-		s->buildKnobMesh();
 		if (s->onValueChanged) s->onValueChanged(s->name, s->value);
 		return true;
 	}
@@ -1796,7 +1802,6 @@ namespace ZL {
 				if (t > 1.0f) t = 1.0f;
 				s->value = t;
 				s->buildTrackMesh();
-				s->buildKnobMesh();
 				if (s->onValueChanged) s->onValueChanged(s->name, s->value);
 			}
 		}
@@ -1843,7 +1848,6 @@ namespace ZL {
 				if (t > 1.0f) t = 1.0f;
 				s->value = t;
 				s->buildTrackMesh();
-				s->buildKnobMesh();
 				if (s->onValueChanged) s->onValueChanged(s->name, s->value);
 				break;
 			}