Aspect-preserving texture fitting now working

Abandoned the original plan to calculate the required scale factors in
TextureProjection::fitTexture(); this turned out to be non-trivial as it would
require a calculation involving the effective aspect ratio of the selected face
in texture space.

Instead, this is done very simply at the GUI level by propagating the
calculated scale factor from the fitted axis to the non-fitted axis, in the
same way a user might achieve this effect manually by copy-pasting scale values
between the respective numeric entry fields.

radiant/ui/surfaceinspector/SurfaceInspector.cpp

@@ -627,17 +627,31 @@ void SurfaceInspector::fitTexture(Axis axis)
 
 	if (repeatX > 0.0 && repeatY > 0.0)
 	{
-        // User-specified fit values must always be >0, but we use -1 internally
-        // to signal not to fit on a particular axis.
-        GlobalCommandSystem().executeCommand("FitTexture",
-                                             (axis == Axis::Y ? -1 : repeatX),
-                                             (axis == Axis::X ? -1 : repeatY));
+        GlobalCommandSystem().executeCommand("FitTexture", repeatX, repeatY);
     }
 	else
 	{
 		// Invalid repeatX && repeatY values
 		wxutil::Messagebox::ShowError(_("Both fit values must be > 0."));
+        return;
 	}
+
+    // If only fitting on a single axis, propagate the scale factor for the
+    // fitted axis to the non-fitted axis, which should preserve the texture
+    // aspect ratio.
+    if (axis != Axis::BOTH)
+    {
+        GlobalSelectionSystem().foreachFace(
+            [&](IFace& face) {
+                ShiftScaleRotation texdef = face.getShiftScaleRotation();
+                if (axis == Axis::X)
+                    texdef.scale[1] = texdef.scale[0];
+                else
+                    texdef.scale[0] = texdef.scale[1];
+                face.setShiftScaleRotation(texdef);
+            }
+        );
+    }
 }
 
 void SurfaceInspector::onFit(Axis axis)

radiantcore/brush/TextureProjection.cpp

@@ -201,12 +201,8 @@ void TextureProjection::fitTexture(std::size_t width, std::size_t height,
     bounds.extents.z() = 1;
 
     // the bounds of a perfectly fitted texture transform
-    AABB perfect(Vector3(s_repeat > 0 ? s_repeat * 0.5 : bounds.origin.x(),
-                         t_repeat > 0 ? t_repeat * 0.5 : bounds.origin.y(),
-                         0),
-                 Vector3(s_repeat > 0 ? s_repeat * 0.5 : bounds.extents.x(),
-                         t_repeat > 0 ? t_repeat * 0.5 : bounds.extents.y(),
-                         1));
+    AABB perfect(Vector3(s_repeat * 0.5, t_repeat * 0.5, 0),
+                 Vector3(s_repeat * 0.5, t_repeat * 0.5, 1));
 
     // the difference between the current texture transform and the perfectly fitted transform
     Matrix4 diffMatrix = Matrix4::getTranslation(bounds.origin - perfect.origin);