Add more tolerance when determining whether to show grid annotations

close to map edges

Author: nyalldawson

src/core/layout/qgslayoutitemmapgrid.cpp

@@ -54,6 +54,8 @@
 
 using namespace Qt::StringLiterals;
 
+#define MAX_GRID_LINES 1000 //maximum number of horizontal or vertical grid lines to draw
+
 QgsLayoutItemMapGridStack::QgsLayoutItemMapGridStack( QgsLayoutItemMap *map )
   : QgsLayoutItemMapItemStack( map )
 {}
@@ -1591,17 +1593,22 @@ void QgsLayoutItemMapGrid::drawCoordinateAnnotation(
     facingLeft = !facingLeft;
     facingRight = !facingRight;
   }
+  const QRectF mapRect = mMap->rect();
   if ( annot.border == Qgis::MapGridBorderSide::Top
-       && ( ( facingLeft && annot.position.x() < mRotatedAnnotationsMarginToCorner ) || ( facingRight && annot.position.x() > mMap->rect().width() - mRotatedAnnotationsMarginToCorner ) ) )
+       && ( ( facingLeft && !qgsDoubleGreaterThanOrNear( annot.position.x(),mRotatedAnnotationsMarginToCorner,ANNOTATION_CLOSE_TO_EDGE_TOLERANCE_MM) )
+            || ( facingRight && !qgsDoubleLessThanOrNear( annot.position.x(), mapRect.width() - mRotatedAnnotationsMarginToCorner, ANNOTATION_CLOSE_TO_EDGE_TOLERANCE_MM ) ) ) )
     return;
   if ( annot.border == Qgis::MapGridBorderSide::Bottom
-       && ( ( facingLeft && annot.position.x() > mMap->rect().width() - mRotatedAnnotationsMarginToCorner ) || ( facingRight && annot.position.x() < mRotatedAnnotationsMarginToCorner ) ) )
+       && ( ( facingLeft && !qgsDoubleLessThanOrNear( annot.position.x(), mapRect.width() - mRotatedAnnotationsMarginToCorner, ANNOTATION_CLOSE_TO_EDGE_TOLERANCE_MM ) )
+            || ( facingRight && !qgsDoubleGreaterThanOrNear( annot.position.x(), mRotatedAnnotationsMarginToCorner, ANNOTATION_CLOSE_TO_EDGE_TOLERANCE_MM ) ) ) )
     return;
   if ( annot.border == Qgis::MapGridBorderSide::Left
-       && ( ( facingLeft && annot.position.y() > mMap->rect().height() - mRotatedAnnotationsMarginToCorner ) || ( facingRight && annot.position.y() < mRotatedAnnotationsMarginToCorner ) ) )
+       && ( ( facingLeft && !qgsDoubleLessThanOrNear( annot.position.y(), mapRect.height() - mRotatedAnnotationsMarginToCorner, ANNOTATION_CLOSE_TO_EDGE_TOLERANCE_MM ) )
+            || ( facingRight && !qgsDoubleGreaterThanOrNear( annot.position.y(), mRotatedAnnotationsMarginToCorner, ANNOTATION_CLOSE_TO_EDGE_TOLERANCE_MM ) ) ) )
     return;
   if ( annot.border == Qgis::MapGridBorderSide::Right
-       && ( ( facingLeft && annot.position.y() < mRotatedAnnotationsMarginToCorner ) || ( facingRight && annot.position.y() > mMap->rect().height() - mRotatedAnnotationsMarginToCorner ) ) )
+       && ( ( facingLeft && !qgsDoubleGreaterThanOrNear( annot.position.y(), mRotatedAnnotationsMarginToCorner, ANNOTATION_CLOSE_TO_EDGE_TOLERANCE_MM ) )
+            || ( facingRight && !qgsDoubleLessThanOrNear( annot.position.y(), mapRect.height() - mRotatedAnnotationsMarginToCorner, ANNOTATION_CLOSE_TO_EDGE_TOLERANCE_MM ) ) ) )
     return;
 
   // adjust to account for text alignment -- for left/right borders the alignment
@@ -1882,14 +1889,16 @@ void QgsLayoutItemMapGrid::calculateXGridLines() const
   }
 
   double currentLevel = static_cast< int >( ( mapBoundingRect.top() - gridOffsetY ) / gridIntervalY ) * gridIntervalY + gridOffsetY;
+  if ( !qgsDoubleGreaterThanOrNear( currentLevel, mapBoundingRect.top(), GRID_LINE_CLOSE_TO_EDGE_TOLERANCE_MAP_UNITS ) )
+    currentLevel += gridIntervalY;
 
   int gridLineCount = 0;
   if ( qgsDoubleNear( mMap->mapRotation(), 0.0 ) || ( mGridUnit != Qgis::MapGridUnit::MapUnits && mGridUnit != Qgis::MapGridUnit::DynamicPageSizeBased ) )
   {
     //no rotation. Do it 'the easy way'
 
     double yCanvasCoord;
-    while ( currentLevel <= mapBoundingRect.bottom() && gridLineCount < MAX_GRID_OBJECTS )
+    while ( qgsDoubleLessThanOrNear( currentLevel, mapBoundingRect.bottom(), GRID_LINE_CLOSE_TO_EDGE_TOLERANCE_MAP_UNITS ) && gridLineCount < MAX_GRID_OBJECTS )
     {
       yCanvasCoord = mMap->rect().height() * ( 1 - ( currentLevel - mapBoundingRect.top() ) / mapBoundingRect.height() );
       GridLine newLine;
@@ -1978,13 +1987,15 @@ void QgsLayoutItemMapGrid::calculateYGridLines() const
   }
 
   double currentLevel = static_cast< int >( ( mapBoundingRect.left() - gridOffsetX ) / gridIntervalX ) * gridIntervalX + gridOffsetX;
+  if ( !qgsDoubleGreaterThanOrNear( currentLevel, mapBoundingRect.left(), GRID_LINE_CLOSE_TO_EDGE_TOLERANCE_MAP_UNITS ) )
+    currentLevel += gridIntervalX;
 
   int gridLineCount = 0;
   if ( qgsDoubleNear( mMap->mapRotation(), 0.0 ) || ( mGridUnit != Qgis::MapGridUnit::MapUnits && mGridUnit != Qgis::MapGridUnit::DynamicPageSizeBased ) )
   {
     //no rotation. Do it 'the easy way'
     double xCanvasCoord;
-    while ( currentLevel <= mapBoundingRect.right() && gridLineCount < MAX_GRID_OBJECTS )
+    while ( qgsDoubleLessThanOrNear( currentLevel, mapBoundingRect.right(), GRID_LINE_CLOSE_TO_EDGE_TOLERANCE_MAP_UNITS ) && gridLineCount < MAX_GRID_OBJECTS )
     {
       xCanvasCoord = mMap->rect().width() * ( currentLevel - mapBoundingRect.left() ) / mapBoundingRect.width();
 

src/core/layout/qgslayoutitemmapgrid.h

@@ -958,6 +958,12 @@ class CORE_EXPORT QgsLayoutItemMapGrid : public QgsLayoutItemMapItem
         }
     };
 
+    static constexpr double GRID_LINE_CLOSE_TO_EDGE_TOLERANCE_MAP_UNITS = 0.00001;
+
+    // we need a little bit of tolerance for showing annotations right at the extremities of their edges,
+    // as we don't want to omit annotations right at the map edges if rounding errors have occurred in the position math
+    static constexpr double ANNOTATION_CLOSE_TO_EDGE_TOLERANCE_MM = 0.01;
+
     struct GridLineAnnotation
     {
         Qgis::MapGridBorderSide border = Qgis::MapGridBorderSide::Left; // border on which the annotation is