Snap to grid (#3016)

* Add widget to side panel

* Draw grid

* snap tool to grid

* Update french translation

* Format code with clang-format

Co-authored-by: joshua <joshua@qelectrotech.org>

src/widgets/capture/capturewidget.cpp

@@ -393,6 +393,18 @@ void CaptureWidget::xywhTick()
     repaint();
 }
 
+void CaptureWidget::onDisplayGridChanged(bool display)
+{
+    m_displayGrid = display;
+    repaint();
+}
+
+void CaptureWidget::onGridSizeChanged(int size)
+{
+    m_gridSize = size;
+    repaint();
+}
+
 void CaptureWidget::showxywh(bool show)
 {
     int timeout =
@@ -605,6 +617,31 @@ void CaptureWidget::paintEvent(QPaintEvent* paintEvent)
                          xy);
     }
 
+    if (m_displayGrid) {
+        painter.save();
+        QColor uicolor = ConfigHandler().uiColor();
+        uicolor.setAlpha(100);
+        painter.setPen(uicolor);
+        painter.setBrush(QBrush(uicolor));
+
+        auto topLeft = mapToGlobal(m_context.selection.topLeft());
+        topLeft.rx() -= topLeft.x() % m_gridSize;
+        topLeft.ry() -= topLeft.y() % m_gridSize;
+        topLeft = mapFromGlobal(topLeft);
+
+        const auto scale{ m_context.screenshot.devicePixelRatio() };
+        const auto step{ m_gridSize * scale };
+        const auto radius{ 1 * scale };
+
+        for (int y = topLeft.y(); y < m_context.selection.bottom(); y += step) {
+            for (int x = topLeft.x(); x < m_context.selection.right();
+                 x += step) {
+                painter.drawEllipse(x, y, radius, radius);
+            }
+        }
+        painter.restore();
+    }
+
     if (m_activeTool && m_mouseIsClicked) {
         m_activeTool->process(painter, m_context.screenshot);
     } else if (m_previewEnabled && activeButtonTool() &&
@@ -671,7 +708,8 @@ bool CaptureWidget::startDrawObjectTool(const QPoint& pos)
                 &CaptureTool::requestAction,
                 this,
                 &CaptureWidget::handleToolSignal);
-        m_context.mousePos = pos;
+
+        m_context.mousePos = m_displayGrid ? snapToGrid(pos) : pos;
         m_activeTool->drawStart(m_context);
         // TODO this is the wrong place to do this
 
@@ -847,7 +885,8 @@ void CaptureWidget::mouseMoveEvent(QMouseEvent* e)
         if (m_adjustmentButtonPressed) {
             m_activeTool->drawMoveWithAdjustment(e->pos());
         } else {
-            m_activeTool->drawMove(e->pos());
+            m_activeTool->drawMove(m_displayGrid ? snapToGrid(e->pos())
+                                                 : e->pos());
         }
         // update drawing object
         updateTool(m_activeTool);
@@ -1126,6 +1165,14 @@ void CaptureWidget::initPanel()
             &SidePanelWidget::togglePanel,
             m_panel,
             &UtilityPanel::toggle);
+    connect(m_sidePanel,
+            &SidePanelWidget::displayGridChanged,
+            this,
+            &CaptureWidget::onDisplayGridChanged);
+    connect(m_sidePanel,
+            &SidePanelWidget::gridSizeChanged,
+            this,
+            &CaptureWidget::onGridSizeChanged);
     // TODO replace with a CaptureWidget signal
     emit m_sidePanel->colorChanged(m_context.color);
     emit toolSizeChanged(m_context.toolSize);
@@ -1721,6 +1768,20 @@ CaptureTool::Type CaptureWidget::activeButtonToolType() const
     return activeTool->type();
 }
 
+QPoint CaptureWidget::snapToGrid(const QPoint& point) const
+{
+    QPoint snapPoint = mapToGlobal(point);
+
+    const auto scale{ m_context.screenshot.devicePixelRatio() };
+
+    snapPoint.setX((qRound(snapPoint.x() / double(m_gridSize)) * m_gridSize) *
+                   scale);
+    snapPoint.setY((qRound(snapPoint.y() / double(m_gridSize)) * m_gridSize) *
+                   scale);
+
+    return mapFromGlobal(snapPoint);
+}
+
 QPointer<CaptureTool> CaptureWidget::activeToolObject()
 {
     return m_captureToolObjects.at(m_panel->activeLayerIndex());