From 1d978ce9fafd2658121a48288a6ddf16cfccecc6 Mon Sep 17 00:00:00 2001
From: Jaakko Keränen <jaakko.keranen@iki.fi>
Date: Tue, 8 Feb 2022 11:53:06 +0200
Subject: 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.
---
 src/ui/documentwidget.c | 35 +++++++++++++++++++++++++++--------
 1 file changed, 27 insertions(+), 8 deletions(-)

(limited to 'src/ui')

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;
                     }
                 }
-- 
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