Fix multiple memory leaks found with LeakSanitizer.

src/draw.cpp

@@ -389,6 +389,8 @@ void GraphicsWindow::HitTestMakeSelection(Point2d mp) {
         }
     }
 
+    canvas.Clear();
+
     if(!s.Equals(&hover)) {
         hover = s;
         PaintGraphics();
@@ -787,5 +789,6 @@ void GraphicsWindow::Paint() {
     }
 
     canvas.EndFrame();
+    canvas.Clear();
 #endif
 }

src/drawconstraint.cpp

@@ -1187,19 +1187,21 @@ void Constraint::Draw(DrawAs how, Canvas *canvas) {
 }
 
 Vector Constraint::GetLabelPos(const Camera &camera) {
+    Vector p;
+
     ObjectPicker canvas = {};
     canvas.camera = camera;
-
-    Vector p;
     DoLayout(DrawAs::DEFAULT, &canvas, &p, NULL);
+    canvas.Clear();
+
     return p;
 }
 
 void Constraint::GetReferencePoints(const Camera &camera, std::vector<Vector> *refs) {
     ObjectPicker canvas = {};
     canvas.camera = camera;
-
     DoLayout(DrawAs::DEFAULT, &canvas, NULL, refs);
+    canvas.Clear();
 }
 
 bool Constraint::IsStylable() const {

src/drawentity.cpp

@@ -126,14 +126,17 @@ void Entity::GetReferencePoints(std::vector<Vector> *refs) {
 }
 
 int Entity::GetPositionOfPoint(const Camera &camera, Point2d p) {
+    int position;
+
     ObjectPicker canvas = {};
     canvas.camera      = camera;
     canvas.point       = p;
     canvas.minDistance = 1e12;
-
     Draw(DrawAs::DEFAULT, &canvas);
+    position = canvas.position;
+    canvas.Clear();
 
-    return canvas.position;
+    return position;
 }
 
 bool Entity::IsStylable() const {

src/export.cpp

@@ -220,6 +220,8 @@ void SolveSpaceUI::ExportViewOrWireframeTo(const std::string &filename, bool exp
             for(Constraint &c : SK.constraint) {
                 c.Draw(Constraint::DrawAs::DEFAULT, &canvas);
             }
+
+            canvas.Clear();
         }
     }
 

src/textwin.cpp

@@ -858,6 +858,7 @@ void TextWindow::Paint() {
     DrawOrHitTestColorPicker(&uiCanvas, PAINT, false, 0, 0);
 
     canvas.EndFrame();
+    canvas.Clear();
 #endif
 }