From 2156b2f2fb7710b6310204eccd21cae4839f8da4 Mon Sep 17 00:00:00 2001
From: Charles Whittington <charleswhitt@gmail.com>
Date: Wed, 1 Jan 2025 22:16:55 -0500
Subject: [PATCH] Added layer of 'translation' values for horisontal cross-axis
 in RTL

---
 core/pyproject.toml         |  2 +-
 core/src/toga/style/pack.py | 34 +++++++++++++++++++++-------------
 tox.ini                     |  2 +-
 3 files changed, 23 insertions(+), 15 deletions(-)

diff --git a/core/pyproject.toml b/core/pyproject.toml
index f0bba62dcd..322f2e4a70 100644
--- a/core/pyproject.toml
+++ b/core/pyproject.toml
@@ -56,7 +56,7 @@ classifiers = [
     "Topic :: Software Development :: Widget Sets",
 ]
 dependencies = [
-    "travertino >= 0.3.0, < 0.4.0",
+    "travertino",
 ]
 
 [project.optional-dependencies]
diff --git a/core/src/toga/style/pack.py b/core/src/toga/style/pack.py
index 65ae1ffa32..eafeed4e37 100644
--- a/core/src/toga/style/pack.py
+++ b/core/src/toga/style/pack.py
@@ -803,31 +803,39 @@ def _layout_children(
 
         # Pass 4: Set cross-axis position of each child.
 
-        # Translate RTL into left-origin, which effectively flips start/end item
-        # alignment.
-        align_items = self.align_items
+        # The "effective" start, end, and align-items values are normally their "real"
+        # values. However, if the cross-axis is horizontal and text-direction RTL,
+        # they're flipped. This is necessary because final positioning is always set
+        # using a top-left origin, even if the "real" start is on the right.
+        effective_align_items = self.align_items
+
         if cross_start == RIGHT:
-            cross_start = LEFT
+            effective_cross_start = LEFT
+            effective_cross_end = RIGHT
+
+            if self.align_items == START:
+                effective_align_items = END
+            elif self.align_items == END:
+                effective_align_items = START
 
-            if align_items == START:
-                align_items = END
-            elif align_items == END:
-                align_items = START
+        else:
+            effective_cross_start = cross_start
+            effective_cross_end = cross_end
 
         for child in node.children:
             # self._debug(f"PASS 4: {child}")
             extra = cross - (
                 getattr(child.layout, f"content_{cross_name}")
-                + child.style[f"margin_{cross_start}"]
-                + child.style[f"margin_{cross_end}"]
+                + child.style[f"margin_{effective_cross_start}"]
+                + child.style[f"margin_{effective_cross_end}"]
             )
             # self._debug(f"-  {self.direction} extra {cross_name} {extra}")
 
-            if align_items == END:
+            if effective_align_items == END:
                 cross_start_value = extra + child.style[f"margin_{cross_start}"]
                 # self._debug(f"  align {child} to {cross_end}")
 
-            elif align_items == CENTER:
+            elif effective_align_items == CENTER:
                 cross_start_value = (
                     int(extra / 2) + child.style[f"margin_{cross_start}"]
                 )
@@ -837,7 +845,7 @@ def _layout_children(
                 cross_start_value = child.style[f"margin_{cross_start}"]
                 # self._debug(f"  align {child} to {cross_start} ")
 
-            setattr(child.layout, f"content_{cross_start}", cross_start_value)
+            setattr(child.layout, f"content_{effective_cross_start}", cross_start_value)
             # self._debug(f"  {getattr(child.layout, f'content_{cross_start}')=}")
 
         if self.direction == COLUMN:
diff --git a/tox.ini b/tox.ini
index 847c4a8107..e51a26763f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -36,7 +36,7 @@ allowlist_externals =
 commands =
     # TOGA_INSTALL_COMMAND is set to a bash command by the CI workflow
     # Install as editable so parallel runs don't clobber the build directory for each other
-    {env:TOGA_INSTALL_COMMAND:python -m pip install {tox_root}{/}core[dev] {tox_root}{/}dummy}
+    {env:TOGA_INSTALL_COMMAND:python -m pip install {tox_root}{/}core[dev] {tox_root}{/}dummy} {/}Users{/}charles{/}toga_dev{/}travertino
     !cov: python -m pytest {posargs:-vv --color yes}
     cov : python -m coverage run -m pytest {posargs:-vv --color yes}