DocumentWidget: Fixed continuous redraw issue

It was possible that the progressive rendering of runs repeatedly kept drawing the first run of the page (e.g., the top heading).

It should still be investigated if a similar issue can occur in the other direction, when drawing downward. A run may exist on the bottom border of a buffer, too.

1 files changed, 27 insertions, 8 deletions

diff --git a/src/ui/documentwidget.c b/src/ui/documentwidget.c
index 7a1cdabc..dbe29c4e 100644
--- a/src/ui/documentwidget.c
+++ b/src/ui/documentwidget.c
@@ -1656,7 +1656,6 @@ static iBool render_DocumentView_(const iDocumentView *d, iDrawContext *ctx, iBo
             ctx->viewPos      = init_I2(left_Rect(ctx->docBounds) - left_Rect(bounds), -buf->origin);
             //            printf("  buffer %zu: buf vis range %d...%d\n", i, bufVisRange.start, bufVisRange.end);
             if (!prerenderExtra && !isEmpty_Range(&bufVisRange)) {
-                didDraw = iTrue;
                 if (isEmpty_Rangei(buf->validRange)) {
                     /* Fill the required currently visible range (vis). */
                     const iRangei bufVisRange = intersect_Rangei(bufRange, vis);
@@ -1669,26 +1668,46 @@ static iBool render_DocumentView_(const iDocumentView *d, iDrawContext *ctx, iBo
                         extend_GmRunRange_(&meta->runsDrawn);
                         buf->validRange = bufVisRange;
                         //                printf("  buffer %zu valid %d...%d\n", i, bufRange.start, bufRange.end);
+                        didDraw = iTrue;
                     }
                 }
                 else {
                     /* Progressively fill the required runs. */
-                    if (meta->runsDrawn.start) {
+                    if (meta->runsDrawn.start && buf->validRange.start > bufRange.start) {
                         beginTarget_Paint(p, buf->texture);
-                        meta->runsDrawn.start = renderProgressive_GmDocument(d->doc, meta->runsDrawn.start,
-                                                                             -1, iInvalidSize,
-                                                                             bufVisRange,
-                                                                             drawRun_DrawContext_,
-                                                                             ctx);
-                        buf->validRange.start = bufVisRange.start;
+                        iZap(ctx->runsDrawn);
+                        const iGmRun *newStart = renderProgressive_GmDocument(d->doc,
+                                                                              meta->runsDrawn.start,
+                                                                              -1,
+                                                                              iInvalidSize,
+                                                                              bufVisRange,
+                                                                              drawRun_DrawContext_,
+                                                                              ctx);
+                        if (ctx->runsDrawn.start) {
+                            /* Something was actually drawn, so update the valid range. */
+                            const int newTop = top_Rect(ctx->runsDrawn.start->visBounds);
+                            if (newTop != buf->validRange.start) {
+                                didDraw = iTrue;
+//                                printf("render: valid:%d->%d run:%p->%p\n",
+//                                       buf->validRange.start, newTop,
+//                                       meta->runsDrawn.start,
+//                                       ctx->runsDrawn.start); fflush(stdout);
+                                buf->validRange.start = newTop;
+                            }
+                            meta->runsDrawn.start = newStart;
+                        }
                     }
                     if (meta->runsDrawn.end) {
                         beginTarget_Paint(p, buf->texture);
+                        iZap(ctx->runsDrawn);
                         meta->runsDrawn.end = renderProgressive_GmDocument(d->doc, meta->runsDrawn.end,
                                                                            +1, iInvalidSize,
                                                                            bufVisRange,
                                                                            drawRun_DrawContext_,
                                                                            ctx);
+                        if (ctx->runsDrawn.start) {
+                            didDraw = iTrue;
+                        }
                         buf->validRange.end = bufVisRange.end;
                     }
                 }