[gimp/gimp-2-10] app: don't chunk update area when rendering projection synchronously

[Ell <ell src gnome org>]

commit b09498cd7a1d9bc961d2849896d02d9e2c556ab9
Author: Ell <ell_se yahoo com>
Date:   Mon Aug 20 03:00:10 2018 -0400

    app: don't chunk update area when rendering projection synchronously
    
    Add a boolean "chunk" parameter to
    gimp_projection_chunk_render_iteration(), which determines whether
    the work area should be sub-divided into chunks prior to rendering
    (previously, the work area would always be sub-divided.)  Only
    pass TRUE when rendering the projection asynchronously, in the
    render callback, and pass FALSE when rendering the projection
    synchronously, in gimp_projection_finish_draw(), which is called
    when flushing the projection through the GimpPickable interface.
    
    Rendering the projection using as big chunks as possible improves
    performance, while worsening responsiveness.  Since responsiveness
    doesn't matter when rendering synchronously, there's no reason to
    render in chunks.
    
    (cherry picked from commit 105ffc787d2ed5b8cee61bf2accc43c0f00f1358)

 app/core/gimpprojection.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)
---
diff --git a/app/core/gimpprojection.c b/app/core/gimpprojection.c
index fa37f4e755..ad32d175fc 100644
--- a/app/core/gimpprojection.c
+++ b/app/core/gimpprojection.c
@@ -162,7 +162,8 @@ static void        gimp_projection_chunk_render_start    (GimpProjection  *proj)
 static void        gimp_projection_chunk_render_stop     (GimpProjection  *proj);
 static gboolean    gimp_projection_chunk_render_callback (gpointer         data);
 static void        gimp_projection_chunk_render_init     (GimpProjection  *proj);
-static gboolean    gimp_projection_chunk_render_iteration(GimpProjection  *proj);
+static gboolean    gimp_projection_chunk_render_iteration(GimpProjection  *proj,
+                                                          gboolean         chunk);
 static gboolean    gimp_projection_chunk_render_next_area(GimpProjection  *proj);
 static void        gimp_projection_paint_area            (GimpProjection  *proj,
                                                           gboolean         now,
@@ -650,7 +651,7 @@ gimp_projection_finish_draw (GimpProjection *proj)
 
       gimp_projectable_begin_render (proj->priv->projectable);
 
-      while (gimp_projection_chunk_render_iteration (proj));
+      while (gimp_projection_chunk_render_iteration (proj, FALSE));
 
       gimp_projectable_end_render (proj->priv->projectable);
     }
@@ -819,7 +820,7 @@ gimp_projection_chunk_render_callback (gpointer data)
 
   do
     {
-      if (! gimp_projection_chunk_render_iteration (proj))
+      if (! gimp_projection_chunk_render_iteration (proj, TRUE))
         {
           gimp_projection_chunk_render_stop (proj);
 
@@ -907,7 +908,8 @@ gimp_projection_chunk_render_init (GimpProjection *proj)
  * operations.  -- Adam
  */
 static gboolean
-gimp_projection_chunk_render_iteration (GimpProjection *proj)
+gimp_projection_chunk_render_iteration (GimpProjection *proj,
+                                        gboolean        chunk)
 {
   GimpProjectionChunkRender *chunk_render = &proj->priv->chunk_render;
   gint                       work_x       = chunk_render->work_x;
@@ -915,11 +917,14 @@ gimp_projection_chunk_render_iteration (GimpProjection *proj)
   gint                       work_w;
   gint                       work_h;
 
-  work_w = MIN (GIMP_PROJECTION_CHUNK_WIDTH,
-                chunk_render->x + chunk_render->width - work_x);
+  work_w = chunk_render->x + chunk_render->width  - work_x;
+  work_h = chunk_render->y + chunk_render->height - work_y;
 
-  work_h = MIN (GIMP_PROJECTION_CHUNK_HEIGHT,
-                chunk_render->y + chunk_render->height - work_y);
+  if (chunk)
+    work_w = MIN (work_w, GIMP_PROJECTION_CHUNK_WIDTH);
+
+  if (chunk || work_x != chunk_render->x)
+    work_h = MIN (work_h, GIMP_PROJECTION_CHUNK_HEIGHT);
 
   gimp_projection_paint_area (proj, TRUE /* sic! */,
                               work_x, work_y, work_w, work_h);