Progressive document rendering

VisBuf now guarantees that all the buffers are sequentially ordered. This ensure complete utilization of all the buffers. Previously some buffers were not used at all, or allocated to the same origin as another one (!).

DocumentWidget is able to progressively fill up a buffer while scrolling. After any change to the visible region has been detected (and there are no ongoing changes), prerender the remaining runs one at a time. This solves the issue where one text run would be always unnecessarily rendered while scrolling, even if the scroll distance was just one pixel.

1 files changed, 8 insertions, 2 deletions

diff --git a/src/ui/visbuf.h b/src/ui/visbuf.h
index b285e90b..7efa36a7 100644
--- a/src/ui/visbuf.h
+++ b/src/ui/visbuf.h
@@ -33,12 +33,16 @@ struct Impl_VisBufTexture {
     SDL_Texture *texture;
     int origin;
     iRangei validRange;
+    void *user;
 };
 
+#define numBuffers_VisBuf   ((size_t) 4)
+
 struct Impl_VisBuf {
     iInt2 texSize;
     iRangei vis;
-    iVisBufTexture buffers[4];
+    iVisBufTexture buffers[numBuffers_VisBuf];
+    void (*bufferInvalidated)(iVisBuf *, size_t index);
 };
 
 iDeclareTypeConstruction(VisBuf)
@@ -46,8 +50,10 @@ iDeclareTypeConstruction(VisBuf)
 void    invalidate_VisBuf       (iVisBuf *);
 void    alloc_VisBuf            (iVisBuf *, const iInt2 size, int granularity);
 void    dealloc_VisBuf          (iVisBuf *);
-void    reposition_VisBuf       (iVisBuf *, const iRangei vis);
+iBool   reposition_VisBuf       (iVisBuf *, const iRangei vis); /* returns true if `vis` changes */
 void    validate_VisBuf         (iVisBuf *);
 
+iRangei allocRange_VisBuf       (const iVisBuf *);
+iRangei bufferRange_VisBuf      (const iVisBuf *, size_t index);
 void    invalidRanges_VisBuf    (const iVisBuf *, const iRangei full, iRangei *out_invalidRanges);
 void    draw_VisBuf             (const iVisBuf *, iInt2 topLeft);