Do not modify the changed() status of rows when no drawing has taken place

There are several places in the code where a row is painted with drawing disabled in the painter. The goal is only to recompute inset positions.

Such a case happens in BufferView::checkCursorScrollOffset, as part of the horizontal scrolling patch. Note that this particular piece of code should eventually be removed, since it is a performance problem.

It makes sense to consider that only a real painting of a row should change its status. However, I would not be surprised if this change would break other things.

Fixes: #9388

diff --git a/src/BufferView.cpp b/src/BufferView.cpp
index fd2042ffde58e4be665fb2206fa8a3f6171efcde..7cb99cdf4d9cb298a2d34370e71057e14c5320ab 100644 (file)
--- a/src/BufferView.cpp
+++ b/src/BufferView.cpp
@@ -2970,6 +2970,19 @@ void BufferView::checkCursorScrollOffset(PainterInfo & pi)
        // Set the row on which the cursor lives.
        setCurrentRowSlice(rowSlice);
 
+       /** FIXME: the code below adds an extraneous computation of inset
+        * positions, and can therefore be bad for performance (think for
+        * example about a very large tabular inset. Redawing the row
+        * where it is means redrawing the whole screen).
+        *
+        * The bug that this fixes is the following: assume that there is
+        * a very large math inset. Upon entering the inset, when pressing
+        * `End', the row is not scrolled and the cursor is not visible. I
+        * am not sure why the extra row computation fixes the problem,
+        * actually.
+        *
+        * A proper fix should be found and this code should be removed.
+        */
        // Force the recomputation of inset positions
        bool const drawing = pi.pain.isDrawingEnabled();
        pi.pain.setDrawingEnabled(false);
@@ -2978,6 +2991,7 @@ void BufferView::checkCursorScrollOffset(PainterInfo & pi)
                      -d->horiz_scroll_offset_, 0);
        rp.paintText();
        pi.pain.setDrawingEnabled(drawing);
+       /** END of bad code */
 
        // Current x position of the cursor in pixels
        int const cur_x = getPos(d->cursor_).x_;

diff --git a/src/TextMetrics.cpp b/src/TextMetrics.cpp
index f29202c668644dc6dada33af211f7fd25ac7435b..2119f8ed16037416359c9792d3187e8878516310 100644 (file)
--- a/src/TextMetrics.cpp
+++ b/src/TextMetrics.cpp
@@ -1878,7 +1878,8 @@ void TextMetrics::drawParagraph(PainterInfo & pi, pit_type const pit, int const
                }
 
                // Row signature; has row changed since last paint?
-               row.setCrc(pm.computeRowSignature(row, bparams));
+               if (pi.pain.isDrawingEnabled())
+                       row.setCrc(pm.computeRowSignature(row, bparams));
                bool row_has_changed = row.changed()
                        || rowSlice == bv_->lastRowSlice();
 
@@ -1916,7 +1917,8 @@ void TextMetrics::drawParagraph(PainterInfo & pi, pit_type const pit, int const
                        LYXERR(Debug::PAINTING, foreword << "pit=" << pit << " row=" << i
                                << " row_selection="    << row.selection()
                                << " full_repaint="     << pi.full_repaint
-                               << " row_has_changed="  << row_has_changed);
+                               << " row_has_changed="  << row_has_changed
+                               << " drawingEnabled=" << pi.pain.isDrawingEnabled());
                }
 
                // Backup full_repaint status and force full repaint