VisBuf: Increase buffer size for scrolling; fixed glitches

Instead of 1.5x coverage, the buffer now has a full 2x.

4 files changed, 56 insertions, 30 deletions

diff --git a/src/ui/documentwidget.c b/src/ui/documentwidget.c
index 3b5ddb7c..07b359da 100644
--- a/src/ui/documentwidget.c
+++ b/src/ui/documentwidget.c
@@ -2040,10 +2040,9 @@ static iBool handleCommand_DocumentWidget_(iDocumentWidget *d, const char *cmd)
             fetchNextUnfetchedImage_DocumentWidget_(d)) {
             return iTrue;
         }
-        const float amount = argLabel_Command(cmd, "full") ? 1.0f : 0.5f;
+        const float amount = argLabel_Command(cmd, "full") != 0 ? 1.0f : 0.5f;
         smoothScroll_DocumentWidget_(d,
-                                     dir * (amount * height_Rect(documentBounds_DocumentWidget_(d)) -
-                                            0 * lineHeight_Text(paragraph_FontId)),
+                                     dir * amount * height_Rect(documentBounds_DocumentWidget_(d)),
                                      smoothDuration_DocumentWidget_);
         return iTrue;
     }
@@ -3391,7 +3390,7 @@ static void draw_DocumentWidget_(const iDocumentWidget *d) {
     const iRangei vis  = visibleRange_DocumentWidget_(d);
     const iRangei full = { 0, size_GmDocument(d->doc).y };
     reposition_VisBuf(visBuf, vis);
-    iRangei invalidRange[3];
+    iRangei invalidRange[iElemCount(d->visBuf->buffers)];
     invalidRanges_VisBuf(visBuf, full, invalidRange);
     /* Redraw the invalid ranges. */ {
         iPaint *p = &ctx.paint;
diff --git a/src/ui/listwidget.c b/src/ui/listwidget.c
index 942c46dd..95a59090 100644
--- a/src/ui/listwidget.c
+++ b/src/ui/listwidget.c
@@ -361,17 +361,18 @@ static void draw_ListWidget_(const iListWidget *d) {
         /* TODO: This seems to draw two items per each shift of the visible region, even though
            one should be enough. Probably an off-by-one error in the calculation of the
            invalid range. */
-        iAssert(d->visBuf->buffers[0].texture);
-        iAssert(d->visBuf->buffers[1].texture);
-        iAssert(d->visBuf->buffers[2].texture);
-        const int bg[3] = { w->bgColor, w->bgColor, w->bgColor };
-//        const int bg[3] = { red_ColorId, magenta_ColorId, blue_ColorId };
+        iForIndices(i, d->visBuf->buffers) {
+            iAssert(d->visBuf->buffers[i].texture);
+        }
+        const int bg[iElemCount(d->visBuf->buffers)] = {
+            w->bgColor, w->bgColor, w->bgColor, w->bgColor
+        };
         const int bottom = numItems_ListWidget(d) * d->itemHeight;
         const iRangei vis = { d->scrollY / d->itemHeight * d->itemHeight,
                              ((d->scrollY + bounds.size.y) / d->itemHeight + 1) * d->itemHeight };
         reposition_VisBuf(d->visBuf, vis);
         /* Check which parts are invalid. */
-        iRangei invalidRange[3];
+        iRangei invalidRange[iElemCount(d->visBuf->buffers)];
         invalidRanges_VisBuf(d->visBuf, (iRangei){ 0, bottom }, invalidRange);
         iForIndices(i, d->visBuf->buffers) {
             iVisBufTexture *buf = &d->visBuf->buffers[i];
diff --git a/src/ui/visbuf.c b/src/ui/visbuf.c
index 0f9e1092..198ad574 100644
--- a/src/ui/visbuf.c
+++ b/src/ui/visbuf.c
@@ -75,12 +75,13 @@ void dealloc_VisBuf(iVisBuf *d) {
 void reposition_VisBuf(iVisBuf *d, const iRangei vis) {
     d->vis = vis;
     iRangei good = { 0, 0 };
-    size_t avail[3], numAvail = 0;
+    size_t avail[iElemCount(d->buffers)], numAvail = 0;
     /* Check which buffers are available for reuse. */ {
         iForIndices(i, d->buffers) {
-            iVisBufTexture *buf = d->buffers + i;
-            const iRangei region = { buf->origin, buf->origin + d->texSize.y };
-            if (region.start >= vis.end || region.end <= vis.start) {
+            iVisBufTexture *buf    = d->buffers + i;
+            const iRangei   region = { buf->origin, buf->origin + d->texSize.y };
+            if (isEmpty_Rangei(buf->validRange) ||
+                buf->validRange.start >= vis.end || buf->validRange.end <= vis.start) {
                 avail[numAvail++] = i;
                 iZap(buf->validRange);
             }
@@ -89,25 +90,50 @@ void reposition_VisBuf(iVisBuf *d, const iRangei vis) {
             }
         }
     }
-    if (numAvail == iElemCount(d->buffers)) {
-        /* All buffers are outside the visible range, do a reset. */
-        d->buffers[0].origin = vis.start;
-        d->buffers[1].origin = vis.start + d->texSize.y;
-        d->buffers[2].origin = vis.start + 2 * d->texSize.y;
+    iBool wasChanged = iFalse;
+    iBool doReset    = (numAvail == iElemCount(d->buffers));
+    /* Try to extend to cover the visible range. */
+    while (!doReset && vis.start < good.start) {
+        if (numAvail == 0) {
+            doReset = iTrue;
+            break;
+        }
+        good.start -= d->texSize.y;
+        d->buffers[avail[--numAvail]].origin = good.start;
+        wasChanged = iTrue;
     }
-    else {
-        /* Extend to cover the visible range. */
-        while (vis.start < good.start) {
-            iAssert(numAvail > 0);
-            d->buffers[avail[--numAvail]].origin = good.start - d->texSize.y;
-            good.start -= d->texSize.y;
+    while (!doReset && vis.end > good.end) {
+        if (numAvail == 0) {
+            doReset = iTrue;
+            break;
         }
-        while (vis.end > good.end) {
-            iAssert(numAvail > 0);
-            d->buffers[avail[--numAvail]].origin = good.end;
-            good.end += d->texSize.y;
+        d->buffers[avail[--numAvail]].origin = good.end;
+        good.end += d->texSize.y;
+        wasChanged = iTrue;
+    }
+    if (doReset) {
+//        puts("VisBuf reset!");
+//        fflush(stdout);
+        wasChanged = iTrue;
+        int pos = -1;
+        iForIndices(i, d->buffers) {
+            iZap(d->buffers[i].validRange);
+            d->buffers[i].origin = vis.start + pos++ * d->texSize.y;
         }
     }
+#if 0
+    if (wasChanged) {
+        printf("\nVISIBLE RANGE: %d ... %d\n", vis.start, vis.end);
+        iForIndices(i, d->buffers) {
+            const iVisBufTexture *bt = &d->buffers[i];
+            printf(" %zu: buf %5d ... %5d  valid %5d ... %5d\n", i, bt->origin,
+                   bt->origin + d->texSize.y,
+                   bt->validRange.start,
+                   bt->validRange.end);
+        }
+        fflush(stdout);
+    }
+#endif
 }
 
 void invalidRanges_VisBuf(const iVisBuf *d, const iRangei full, iRangei *out_invalidRanges) {
diff --git a/src/ui/visbuf.h b/src/ui/visbuf.h
index 4b0908f9..b285e90b 100644
--- a/src/ui/visbuf.h
+++ b/src/ui/visbuf.h
@@ -38,7 +38,7 @@ struct Impl_VisBufTexture {
 struct Impl_VisBuf {
     iInt2 texSize;
     iRangei vis;
-    iVisBufTexture buffers[3];
+    iVisBufTexture buffers[4];
 };
 
 iDeclareTypeConstruction(VisBuf)