Don't allocate all of memory when the coord system turns inside out.

Fixes https://gitlab.com/kicad/code/kicad/issues/14088

common/widgets/mathplot.cpp

@@ -572,22 +572,31 @@ void mpFXY::Plot( wxDC& dc, mpWindow& w )
 
     wxCHECK_RET( m_scaleY, wxS( "Y scale was not set" ) );
 
-    if( m_visible )
+    if( !m_visible )
-    {
+        return;
-        dc.SetPen( m_pen );
-
-        double x, y;
-        // Do this to reset the counters to evaluate bounding box for label positioning
-        Rewind(); GetNextXY( x, y );
-        maxDrawX = x; minDrawX = x; maxDrawY = y; minDrawY = y;
-        // drawnPoints = 0;
-        Rewind();
 
     wxCoord startPx = m_drawOutsideMargins ? 0 : w.GetMarginLeft();
     wxCoord endPx   = m_drawOutsideMargins ? w.GetScrX() : w.GetScrX() - w.GetMarginRight();
     wxCoord minYpx  = m_drawOutsideMargins ? 0 : w.GetMarginTop();
     wxCoord maxYpx  = m_drawOutsideMargins ? w.GetScrY() : w.GetScrY() - w.GetMarginBottom();
 
+    // Check for a collapsed window before we try to allocate a negative number of points
+    if( endPx <= startPx || minYpx >= maxYpx )
+        return;
+
+    dc.SetPen( m_pen );
+
+    double x, y;
+    // Do this to reset the counters to evaluate bounding box for label positioning
+    Rewind();
+    GetNextXY( x, y );
+    maxDrawX = x;
+    minDrawX = x;
+    maxDrawY = y;
+    minDrawY = y;
+    // drawnPoints = 0;
+    Rewind();
+
     dc.SetClippingRegion( startPx, minYpx, endPx - startPx + 1, maxYpx - minYpx + 1 );
 
     if( !m_continuous )
@@ -618,19 +627,14 @@ void mpFXY::Plot( wxDC& dc, mpWindow& w )
             for( auto& iy: ys )
             {
                 if( m_drawOutsideMargins
-                        || ( (ix >= startPx) && (ix <= endPx) && (iy >= minYpx)
+                    || ( (ix >= startPx) && (ix <= endPx) && (iy >= minYpx) && (iy <= maxYpx) ) )
-                             && (iy <= maxYpx) ) )
                 {
-                        // for some reason DrawPoint does not use the current pen,
+                    // for some reason DrawPoint does not use the current pen, so we use
-                        // so we use DrawLine for fat pens
+                    // DrawLine for fat pens
                     if( m_pen.GetWidth() <= 1 )
-                        {
                         dc.DrawPoint( ix, iy );
-                        }
                     else
-                        {
                         dc.DrawLine( ix, iy, ix, iy );
-                        }
 
                     UpdateViewBoundary( ix, iy );
                 }
@@ -658,9 +662,9 @@ void mpFXY::Plot( wxDC& dc, mpWindow& w )
         // because at least on Windows dc.DrawLines() can hang for a lot of points.
         // (> 10000 points) (can happens when a lot of points is calculated)
         // To avoid long draw time (and perhaps hanging) one plot only not redundant lines.
-            // To avoid artifacts when skipping points to the same x coordinate, for each
+        // To avoid artifacts when skipping points to the same x coordinate, for each group of
-            // group of points at a give, x coordinate we also draw a vertical line at this coord,
+        // points at a give, x coordinate we also draw a vertical line at this coord, from the
-            // from the ymin to the ymax vertical coordinates of skipped points
+        // ymin to the ymax vertical coordinates of skipped points
         while( GetNextXY( x, y ) )
         {
             double px = m_scaleX->TransformToPlot( x );
@@ -670,8 +674,8 @@ void mpFXY::Plot( wxDC& dc, mpWindow& w )
             wxCoord y1 = w.y2p( py );
 
             // Store only points on the drawing area, to speed up the drawing time
-                // Note: x1 is a value truncated from px by w.x2p(). So to be sure the
+            // Note: x1 is a value truncated from px by w.x2p(). So to be sure the first point
-                // first point is drawn, the x1 low limit is startPx-1 in plot coordinates
+            // is drawn, the x1 low limit is startPx-1 in plot coordinates
             if( x1 >= startPx-1 && x1 <= endPx )
             {
                 if( !count || line_start.x != x1 )
@@ -679,8 +683,8 @@ void mpFXY::Plot( wxDC& dc, mpWindow& w )
                     if( count && dupx0 > 1 && ymin0 != ymax0 )
                     {
                         // Vertical points are merged, draw the pending vertical line
-                            // However, if the line is one pixel length, it is not drawn,
+                        // However, if the line is one pixel length, it is not drawn, because
-                            // because the main trace show this point
+                        // the main trace show this point
                         dc.DrawLine( x0, ymin0, x0, ymax0 );
                     }
 
@@ -706,10 +710,10 @@ void mpFXY::Plot( wxDC& dc, mpWindow& w )
 
         if( pointList.size() > 1 )
         {
-                // For a better look (when using dashed lines) and more optimization,
+            // For a better look (when using dashed lines) and more optimization, try to merge
-                // try to merge horizontal segments, in order to plot longer lines
+            // horizontal segments, in order to plot longer lines
-                // we are merging horizontal segments because this is easy,
+            // We are merging horizontal segments because this is easy, and horizontal segments
-                // and horizontal segments are a frequent cases
+            // are a frequent cases
             std::vector<wxPoint> drawPoints;
             drawPoints.reserve( endPx - startPx + 1 );
 
@@ -717,14 +721,18 @@ void mpFXY::Plot( wxDC& dc, mpWindow& w )
 
             for( size_t ii = 1; ii < pointList.size()-1; ii++ )
             {
-                    // Skip intermediate points between the first point and the last
+                // Skip intermediate points between the first point and the last point of the
-                    // point of the segment candidate
+                // segment candidate
                 if( drawPoints.back().y == pointList[ii].y &&
                     drawPoints.back().y == pointList[ii+1].y )
+                {
                     continue;
+                }
                 else
+                {
                     drawPoints.push_back( pointList[ii] );
                 }
+            }
 
             // push the last point to draw in list
             if( drawPoints.back() != pointList.back() )
@@ -771,7 +779,6 @@ void mpFXY::Plot( wxDC& dc, mpWindow& w )
 
         dc.DrawText( m_name, tx, ty );
     }
-    }
 
     dc.DestroyClippingRegion();
 }