Store dialog geometry in DPI-independent pixels to prevent size ratcheting

On mixed-DPI multi-monitor setups, dialog sizes grow each time they are
reopened because logical pixel values change when a window moves between
monitors with different scaling factors. The std::max comparison during
restore guarantees monotonic growth since the DPI-scaled value always
exceeds the previously saved unscaled value.

Store width and height as DIP (device-independent pixels) using ToDIP()
on save and FromDIP() on restore. This makes the persisted size stable
regardless of which monitor the dialog was on when closed. A "dip" flag
in the JSON differentiates new DIP-format values from legacy logical
pixel values, which are converted in place on first load.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/20120

common/dialog_shim.cpp

@@ -387,6 +387,9 @@ bool DIALOG_SHIM::Show( bool show )
 
         if( savedDialogRect.GetSize().x != 0 && savedDialogRect.GetSize().y != 0 )
         {
+            // Convert saved DIP size to logical pixels for the current monitor
+            wxSize restoredSize = FromDIP( savedDialogRect.GetSize() );
+
             if( m_useCalculatedSize )
             {
                 SetSize( savedDialogRect.GetPosition().x, savedDialogRect.GetPosition().y,
@@ -395,8 +398,8 @@ bool DIALOG_SHIM::Show( bool show )
             else
             {
                 SetSize( savedDialogRect.GetPosition().x, savedDialogRect.GetPosition().y,
-                         std::max( wxDialog::GetSize().x, savedDialogRect.GetSize().x ),
-                         std::max( wxDialog::GetSize().y, savedDialogRect.GetSize().y ), 0 );
+                         std::max( wxDialog::GetSize().x, restoredSize.x ),
+                         std::max( wxDialog::GetSize().y, restoredSize.y ), 0 );
 
                 // Reset minimum size so the user can resize the dialog smaller than
                 // the saved size. We must clear the current minimum and invalidate
@@ -565,12 +568,13 @@ void DIALOG_SHIM::SaveControlState()
     std::string dialogKey = m_hash_key.empty() ? getDialogKeyFromTitle( GetTitle() ) : m_hash_key;
     std::map<std::string, nlohmann::json>& dlgMap = settings->CsInternals().m_dialogControlValues[ dialogKey ];
 
-    wxRect rect( GetPosition(), GetSize() );
+    wxPoint pos = GetPosition();
+    wxSize  dipSize = ToDIP( GetSize() );
     nlohmann::json geom;
-    geom[ "x" ] = rect.GetX();
-    geom[ "y" ] = rect.GetY();
-    geom[ "w" ] = rect.GetWidth();
-    geom[ "h" ] = rect.GetHeight();
+    geom[ "x" ] = pos.x;
+    geom[ "y" ] = pos.y;
+    geom[ "w" ] = dipSize.x;
+    geom[ "h" ] = dipSize.y;
     dlgMap[ "__geometry" ] = geom;
 
     std::function<void( wxWindow* )> saveFn =

common/settings/common_settings.cpp

@@ -38,13 +38,14 @@
 #include <wx/log.h>
 #include <wx/regex.h>
 #include <wx/tokenzr.h>
+#include <wx/window.h>
 
 
 ///! The following environment variables will never be migrated from a previous version
 const wxRegEx versionedEnvVarRegex( wxS( "KICAD[0-9]+_[A-Z0-9_]+(_DIR)?" ) );
 
 ///! Update the schema version whenever a migration is required
-const int commonSchemaVersion = 4;
+const int commonSchemaVersion = 5;
 
 COMMON_SETTINGS::~COMMON_SETTINGS() = default;
 
@@ -482,6 +483,7 @@ COMMON_SETTINGS::COMMON_SETTINGS() :
     registerMigration( 1, 2, std::bind( &COMMON_SETTINGS::migrateSchema1to2, this ) );
     registerMigration( 2, 3, std::bind( &COMMON_SETTINGS::migrateSchema2to3, this ) );
     registerMigration( 3, 4, std::bind( &COMMON_SETTINGS::migrateSchema3to4, this ) );
+    registerMigration( 4, 5, std::bind( &COMMON_SETTINGS::migrateSchema4to5, this ) );
 }
 
 
@@ -661,6 +663,46 @@ bool COMMON_SETTINGS::migrateSchema3to4()
 }
 
 
+bool COMMON_SETTINGS::migrateSchema4to5()
+{
+    try
+    {
+        nlohmann::json& controls = m_internals->At( "dialog" ).at( "controls" );
+
+        for( auto& [dlgKey, dlgVal] : controls.items() )
+        {
+            if( !dlgVal.is_object() )
+                continue;
+
+            auto geoIt = dlgVal.find( "__geometry" );
+
+            if( geoIt == dlgVal.end() || !geoIt->is_object() )
+                continue;
+
+            nlohmann::json& geom = *geoIt;
+
+            // Legacy values were stored in logical pixels. Convert to DIP using the
+            // primary display's scale factor (best approximation without window context).
+            int w = geom.value( "w", 0 );
+            int h = geom.value( "h", 0 );
+
+            wxSize dipSize = wxWindow::ToDIP( wxSize( w, h ), nullptr );
+            geom[ "w" ] = dipSize.x;
+            geom[ "h" ] = dipSize.y;
+
+            geom.erase( "dip" );
+        }
+    }
+    catch( ... )
+    {
+        wxLogTrace( traceSettings,
+                    wxT( "COMMON_SETTINGS::Migrate 4->5: dialog.controls not found" ) );
+    }
+
+    return true;
+}
+
+
 bool COMMON_SETTINGS::MigrateFromLegacy( wxConfigBase* aCfg )
 {
     bool ret = true;

include/settings/common_settings.h

@@ -197,6 +197,7 @@ private:
     bool migrateSchema1to2();
     bool migrateSchema2to3();
     bool migrateSchema3to4();
+    bool migrateSchema4to5();
 
     struct LEGACY_3D_SEARCH_PATH
     {

qa/data/config/10.0/kicad_common.json

@@ -66,7 +66,7 @@
     "zoom_speed_auto": true
   },
   "meta": {
-    "version": 4
+    "version": 5
   },
   "package_manager": {
     "sash_pos": 380