From 4b1ad2dc1748c7c004d8829400a8296efd31576a Mon Sep 17 00:00:00 2001
From: Campbell Barton <ideasman42@gmail.com>
Date: Tue, 26 Oct 2021 00:10:18 +1100
Subject: Fix T92361: Zooming nodes clips text labels

While c7d94a7827a5be9343eea22a9638bb059f185206 exposed this bug,
this was caused by text widths being calculated without taking the zoom
level into account since drawing at a smaller size is often wider than
the width of the larger text scaled by the zoom.
---
 source/blender/editors/include/UI_interface.h      |  7 +++++-
 .../blender/editors/interface/interface_layout.c   |  8 ++++--
 source/blender/editors/interface/interface_style.c | 29 ++++++++++++++++++++++
 3 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/source/blender/editors/include/UI_interface.h b/source/blender/editors/include/UI_interface.h
index de6b975a910..4cd921bc61e 100644
--- a/source/blender/editors/include/UI_interface.h
+++ b/source/blender/editors/include/UI_interface.h
@@ -2687,7 +2687,12 @@ void UI_fontstyle_draw_simple_backdrop(const struct uiFontStyle *fs,
                                        const float col_fg[4],
                                        const float col_bg[4]);
 
-int UI_fontstyle_string_width(const struct uiFontStyle *fs, const char *str);
+int UI_fontstyle_string_width(const struct uiFontStyle *fs,
+                              const char *str) ATTR_WARN_UNUSED_RESULT ATTR_NONNULL(1, 2);
+int UI_fontstyle_string_width_with_block_aspect(const struct uiFontStyle *fs,
+                                                const char *str,
+                                                const float aspect) ATTR_WARN_UNUSED_RESULT
+    ATTR_NONNULL(1, 2);
 int UI_fontstyle_height_max(const struct uiFontStyle *fs);
 
 void UI_draw_icon_tri(float x, float y, char dir, const float[4]);
diff --git a/source/blender/editors/interface/interface_layout.c b/source/blender/editors/interface/interface_layout.c
index e54b261facd..25ba0e13487 100644
--- a/source/blender/editors/interface/interface_layout.c
+++ b/source/blender/editors/interface/interface_layout.c
@@ -351,12 +351,16 @@ static int ui_text_icon_width_ex(uiLayout *layout,
     if (layout->alignment != UI_LAYOUT_ALIGN_EXPAND) {
       layout->item.flag |= UI_ITEM_FIXED_SIZE;
     }
-    const uiFontStyle *fstyle = UI_FSTYLE_WIDGET;
+
     float margin = pad_factor->text;
     if (icon) {
       margin += pad_factor->icon;
     }
-    return UI_fontstyle_string_width(fstyle, name) + (unit_x * margin);
+
+    const float aspect = layout->root->block->aspect;
+    const uiFontStyle *fstyle = UI_FSTYLE_WIDGET;
+    return UI_fontstyle_string_width_with_block_aspect(fstyle, name, aspect) +
+           (int)ceilf(unit_x * margin);
   }
   return unit_x * 10;
 }
diff --git a/source/blender/editors/interface/interface_style.c b/source/blender/editors/interface/interface_style.c
index 6b1ff92a855..2a1cdfd447c 100644
--- a/source/blender/editors/interface/interface_style.c
+++ b/source/blender/editors/interface/interface_style.c
@@ -376,6 +376,35 @@ int UI_fontstyle_string_width(const uiFontStyle *fs, const char *str)
   return (int)BLF_width(fs->uifont_id, str, BLF_DRAW_STR_DUMMY_MAX);
 }
 
+/**
+ * Return the width of `str` with the spacing & kerning of `fs` with `aspect`
+ * (representing #uiBlock.aspect) applied.
+ *
+ * When calculating text width, the UI layout logic calculate widths without scale,
+ * only applying scale when drawing. This causes problems for fonts since kerning at
+ * smaller sizes often makes them wider than a scaled down version of the larger text.
+ * Resolve this by calculating the text at the on-screen size,
+ * returning the result scaled back to 1:1. See T92361.
+ */
+int UI_fontstyle_string_width_with_block_aspect(const uiFontStyle *fs,
+                                                const char *str,
+                                                const float aspect)
+{
+  uiFontStyle fs_buf;
+  if (aspect != 1.0f) {
+    fs_buf = *fs;
+    ui_fontscale(&fs_buf.points, aspect);
+    fs = &fs_buf;
+  }
+
+  int width = UI_fontstyle_string_width(fs, str);
+
+  if (aspect != 1.0f) {
+    width = (int)ceilf(width * aspect);
+  }
+  return width;
+}
+
 int UI_fontstyle_height_max(const uiFontStyle *fs)
 {
   UI_fontstyle_set(fs);
-- 
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