Allow "tapping" when using the Select Rectangle and Select Region tools (#1980)

* Allow "tapping" when using the Select Rectangle and Select Region tools (in a similar way to tapping when drawing)

* Changed the implemetation of "tapping" selection to allow use with a stylus (that generates many more events than a mouse)

Co-authored-by: Luca Citi <lciti@ieee.org>

src/control/tools/Selection.cpp

@@ -84,8 +84,12 @@ void RectSelection::currentPos(double x, double y) {
 
     this->ex = x;
     this->ey = y;
+
+    this->maxDist = std::max({this->maxDist, x - this->sx, this->sx - x, y - this->sy, this->sy - y});
 }
 
+auto RectSelection::userTapped(double zoom) -> bool { return this->maxDist < 10 / zoom; }
+
 void RectSelection::paint(cairo_t* cr, GdkRectangle* rect, double zoom) {
     GtkColorWrapper selectionColor = view->getSelectionColor();
 
@@ -300,3 +304,15 @@ auto RegionSelect::finalize(PageRef page) -> bool {
 
     return !this->selectedElements.empty();
 }
+
+auto RegionSelect::userTapped(double zoom) -> bool {
+    double maxDist = 10 / zoom;
+    auto* r0 = static_cast<RegionPoint*>(this->points->data);
+    for (GList* l = this->points; l != nullptr; l = l->next) {
+        auto* p = static_cast<RegionPoint*>(l->data);
+        if (r0->x - p->x > maxDist || p->x - r0->x > maxDist || r0->y - p->y > maxDist || p->y - r0->y > maxDist) {
+            return false;
+        }
+    }
+    return true;
+}

src/control/tools/Selection.h

@@ -30,6 +30,7 @@ public:
     virtual bool finalize(PageRef page) = 0;
     virtual void paint(cairo_t* cr, GdkRectangle* rect, double zoom) = 0;
     virtual void currentPos(double x, double y) = 0;
+    virtual bool userTapped(double zoom) = 0;
 
 private:
 protected:
@@ -55,12 +56,14 @@ public:
     virtual void paint(cairo_t* cr, GdkRectangle* rect, double zoom);
     virtual void currentPos(double x, double y);
     virtual bool contains(double x, double y);
+    virtual bool userTapped(double zoom);
 
 private:
     double sx;
     double sy;
     double ex;
     double ey;
+    double maxDist = 0;
 
     /**
      * In zoom coordinates
@@ -81,6 +84,7 @@ public:
     virtual void paint(cairo_t* cr, GdkRectangle* rect, double zoom);
     virtual void currentPos(double x, double y);
     virtual bool contains(double x, double y);
+    virtual bool userTapped(double zoom);
 
 private:
     GList* points;

src/gui/PageView.cpp

@@ -534,6 +534,11 @@ auto XojPageView::onButtonReleaseEvent(const PositionInputData& pos) -> bool {
             delete this->selection;
             this->selection = nullptr;
         } else {
+            double zoom = xournal->getZoom();
+            if (this->selection->userTapped(zoom)) {
+                SelectObject select(this);
+                select.at(pos.x / zoom, pos.y / zoom);
+            }
             delete this->selection;
             this->selection = nullptr;