Rebased imstb_rectpack on stb_rect_pack v1.00.

docs/CHANGELOG.txt

@@ -46,6 +46,8 @@ Other Changes:
 - Backends: Vulkan: Added support for specifying multisample count.
   Set ImGui_ImplVulkan_InitInfo::MSAASamples to one of the VkSampleCountFlagBits values
   to use, default is non-multisampled as before. (#2705, #2706) [@vilya]
+- Misc: Updated stb_rect_pack from 0.99 to 1.00 (fixes by @rygorous: off-by-1 bug in best-fit heuristic,
+  fix handling of rectangles too large to fit inside texture). (#2762) [@tido64]
 
 
 -----------------------------------------------------------------------

imstb_rectpack.h

@@ -1,10 +1,10 @@
-// [DEAR IMGUI] 
-// This is a slightly modified version of stb_rect_pack.h 0.99. 
+// [DEAR IMGUI]
+// This is a slightly modified version of stb_rect_pack.h 1.00.
 // Those changes would need to be pushed into nothings/stb:
 // - Added STBRP__CDECL
 // Grep for [DEAR IMGUI] to find the changes.
 
-// stb_rect_pack.h - v0.99 - public domain - rectangle packing
+// stb_rect_pack.h - v1.00 - public domain - rectangle packing
 // Sean Barrett 2014
 //
 // Useful for e.g. packing rectangular textures into an atlas.
@@ -37,9 +37,11 @@
 //    
 //  Bugfixes / warning fixes
 //    Jeremy Jaussaud
+//    Fabian Giesen
 //
 // Version history:
 //
+//     1.00  (2019-02-25)  avoid small space waste; gracefully fail too-wide rectangles
 //     0.99  (2019-02-07)  warning fixes
 //     0.11  (2017-03-03)  return packing success/fail result
 //     0.10  (2016-10-25)  remove cast-away-const to avoid warnings
@@ -357,6 +359,13 @@ static stbrp__findresult stbrp__skyline_find_best_pos(stbrp_context *c, int widt
    width -= width % c->align;
    STBRP_ASSERT(width % c->align == 0);
 
+   // if it can't possibly fit, bail immediately
+   if (width > c->width || height > c->height) {
+      fr.prev_link = NULL;
+      fr.x = fr.y = 0;
+      return fr;
+   }
+
    node = c->active_head;
    prev = &c->active_head;
    while (node->x + width <= c->width) {
@@ -420,7 +429,7 @@ static stbrp__findresult stbrp__skyline_find_best_pos(stbrp_context *c, int widt
          }
          STBRP_ASSERT(node->next->x > xpos && node->x <= xpos);
          y = stbrp__skyline_find_min_y(c, node, xpos, width, &waste);
-         if (y + height < c->height) {
+         if (y + height <= c->height) {
             if (y <= best_y) {
                if (y < best_y || waste < best_waste || (waste==best_waste && xpos < best_x)) {
                   best_x = xpos;