Graph Panel widget: improved the alignment of a graph panel with its …

…neighbours.

Indeed, when running the model in issue #1630, the X axis of the first
graph panel was flashing on macOS for a bit before becoming "stable",
due to our call to xScaleWidget->setMinBorderDist(0, 0). So, we had to
find another way of doing things without that call...

src/plugins/widget/GraphPanelWidget/src/graphpanelplotwidget.cpp

@@ -3252,19 +3252,37 @@ void GraphPanelPlotWidget::alignWithNeighbors(bool pCanReplot,
     axisWidget(QwtPlot::xBottom)->getMinBorderDist(oldMinBorderDistStartX, oldMinBorderDistEndX);
 
     foreach (GraphPanelPlotWidget *plot, selfPlusNeighbors) {
-#if defined(Q_OS_WIN) || defined(Q_OS_LINUX)
-        plot->setUpdatesEnabled(false);
-        // Note #1: this is needed on Windows and Linux otherwise to resize our
-        //          graph panels will result in the X axis flashing due to our
-        //          call to xScaleWidget->setMinBorderDist(0, 0) below...
-        // Note #2: to have this on macOS may result in a graph panel becoming
-        //          black, so we definitely don't want to do it on that
-        //          platform...
-#endif
+        // Determine how much space we should have directly to the left and
+        // right of the X axis
+        // Note: normally, we would initialise minBorderDistStartX and
+        //       minBorderDistEndX with a call to
+        //       xScaleWidget->getBorderDistHint(), but for that call to work as
+        //       expected it would have to preceded by a call to
+        //       xScaleWidget->setMinBorderDist(0, 0). Yet, that call may result
+        //       in one or several graph panels to be refreshed, yielding the X
+        //       axis to be temporarily rendered too far to the left. So, to
+        //       avoid this problem, we initialise minBorderDistStartX and
+        //       minBorderDistEndX with a call to
+        //       xScaleWidget->scaleDraw()->getBorderDistHint() and then
+        //       "manually" check the values of minBorderDistStartX and
+        //       minBorderDistEndX against zero...
 
         QwtScaleWidget *xScaleWidget = plot->axisWidget(QwtPlot::xBottom);
+        int minBorderDistStartX;
+        int minBorderDistEndX;
+
+        xScaleWidget->scaleDraw()->getBorderDistHint(xScaleWidget->font(), minBorderDistStartX, minBorderDistEndX);
+
+        if (minBorderDistStartX < 0)
+            minBorderDistStartX = 0;
+
+        if (minBorderDistEndX < 0)
+            minBorderDistEndX = 0;
+
+        newMinBorderDistStartX = qMax(newMinBorderDistStartX, minBorderDistStartX);
+        newMinBorderDistEndX = qMax(newMinBorderDistEndX, minBorderDistEndX);
 
-        xScaleWidget->setMinBorderDist(0, 0);
+        // Determine how much space we should have to the left of the Y axis
 
         QwtScaleWidget *yScaleWidget = plot->axisWidget(QwtPlot::yLeft);
         QwtScaleDraw *yScaleDraw = yScaleWidget->scaleDraw();
@@ -3275,14 +3293,6 @@ void GraphPanelPlotWidget::alignWithNeighbors(bool pCanReplot,
         // Note: this ensures that our major ticks (which are used to compute
         //       the extent) are up to date...
 
-        int minBorderDistStartX;
-        int minBorderDistEndX;
-
-        xScaleWidget->getBorderDistHint(minBorderDistStartX, minBorderDistEndX);
-
-        newMinBorderDistStartX = qMax(newMinBorderDistStartX, minBorderDistStartX);
-        newMinBorderDistEndX = qMax(newMinBorderDistEndX, minBorderDistEndX);
-
         double minExtentY =  yScaleDraw->extent(yScaleWidget->font())
                             +(plot->titleAxisY().isEmpty()?
                                   0:
@@ -3322,10 +3332,6 @@ void GraphPanelPlotWidget::alignWithNeighbors(bool pCanReplot,
                 replot();
             }
         }
-
-#if defined(Q_OS_WIN) || defined(Q_OS_LINUX)
-        plot->setUpdatesEnabled(true);
-#endif
     }
 }