Smoother edge panning on large selections (#5578)

xournalpp · Mar 22, 2024 · 33fee4c · 33fee4c
1 parent 0543aa4
commit 33fee4c
Showing 1 changed file with 28 additions and 12 deletions.
diff --git a/src/core/control/tools/EditSelection.cpp b/src/core/control/tools/EditSelection.cpp
@@ -796,25 +796,40 @@ bool EditSelection::handleEdgePan(EditSelection* self) {
     const double zoom = self->view->getXournal()->getZoom();
 
     // Helper function to compute scroll amount for a single dimension, based on visible region and selection bbox
-    const auto computeScrollAmt = [&](double visMin, double visLen, double bboxMin, double bboxLen,
-                                      double layoutSize) -> double {
+    const auto computeScrollAmt = [&](double visMin, double visLen, double bboxMin, double bboxLen, double layoutSize,
+                                      double relMousePos) -> double {
         const bool belowMin = bboxMin < visMin;
         const bool aboveMax = bboxMin + bboxLen > visMin + visLen;
         const double visMax = visMin + visLen;
         const double bboxMax = bboxMin + bboxLen;
 
+        const bool isLargeSelection = bboxLen > visLen;
+        const auto centerVis = (visMin + visLen / 2);
+        const auto mouseDiff = (bboxMin + relMousePos * zoom - centerVis);
+
         // Scroll amount multiplier
         double mult = 0.0;
 
-        // Calculate bonus scroll amount due to proportion of selection out of view.
         const double maxMult = settings->getEdgePanMaxMult();
         int panDir = 0;
-        if (aboveMax) {
-            panDir = 1;
-            mult = maxMult * std::min(bboxLen, bboxMax - visMax) / bboxLen;
-        } else if (belowMin) {
-            panDir = -1;
-            mult = maxMult * std::min(bboxLen, visMin - bboxMin) / bboxLen;
+
+        // If the selection is larger than the view, scroll based on mouse position relative to the center of the
+        // visible view Otherwise calculate bonus scroll amount due to proportion of selection out of view.
+        if (isLargeSelection) {
+            mult = maxMult * std::abs(mouseDiff) / (visLen);
+            if (mouseDiff > 0.1 * visLen / 2.0) {
+                panDir = 1;
+            } else if (mouseDiff < -0.1 * visLen / 2.0) {
+                panDir = -1;
+            }
+        } else {
+            if (aboveMax) {
+                panDir = 1;
+                mult = maxMult * std::min(bboxLen, bboxMax - visMax) / bboxLen;
+            } else if (belowMin) {
+                panDir = -1;
+                mult = maxMult * std::min(bboxLen, visMin - bboxMin) / bboxLen;
+            }
         }
 
         // Base amount to translate selection (in document coordinates) per timer tick
@@ -833,14 +848,15 @@ bool EditSelection::handleEdgePan(EditSelection* self) {
 
         return layoutScroll;
     };
-
     // Compute scroll (for layout) and translation (for selection) for x and y
     const int layoutWidth = layout->getMinimalWidth();
     const int layoutHeight = layout->getMinimalHeight();
     const auto visRect = layout->getVisibleRect();
     const auto bbox = self->getBoundingBoxInView();
-    const auto layoutScrollX = computeScrollAmt(visRect.x, visRect.width, bbox.x, bbox.width, layoutWidth);
-    const auto layoutScrollY = computeScrollAmt(visRect.y, visRect.height, bbox.y, bbox.height, layoutHeight);
+    const auto layoutScrollX =
+            computeScrollAmt(visRect.x, visRect.width, bbox.x, bbox.width, layoutWidth, self->relMousePosX);
+    const auto layoutScrollY =
+            computeScrollAmt(visRect.y, visRect.height, bbox.y, bbox.height, layoutHeight, self->relMousePosY);
     const auto translateX = layoutScrollX / zoom;
     const auto translateY = layoutScrollY / zoom;