Error Checker mode: added "Check missing flats" check.
Error Checker mode: fixed several descriptions.
Sprite patches for sprites defined in TEXTURES are now loaded from Sprites namespace.
Some of my older texture alignment code didn't work properly when strict texture/flat handling ("mixtextureflats" game configuration flag set to false) was enabled.
Fixed some incorrect checks for missing texture ("-").
Game Configurations: added "fixedrotation" property to "Polyobject Anchor" (9300), "Polyobject Start Spot" (9301), "Polyobject Start Spot (crush)" (9302) and "Polyobject Start Spot (hurts to touch)" (9303) actors.
Color Picker plugin: moved plugin button to "Modes" toolbar group.
API: added ToolbarSection.Modes property, which can be used in MainForm.AddButton() to add a button to Modes group.
Removed a bunch of unused variables.
Configurations: all 64 game configuration are now available by default.
Game Configurations window: game configurations can now be disabled. This setting is mostly cosmetic. When a game configuration is disabled, it won't be shown in "game configuration" dropdowns in New\Open Map Options and Map Options windows. If a map's .dbs file specifies a disabled configuration, it will be picked as a map configuration anyway.
Linedefs mode: vertex insert preview logic used Highlight range instead of Stitch range (which is used when draw mode engages).
Visual mode: double-sided middle textures were not selected when using "Select" action with "with same texture" modifier.
Textures: some optimizations in patch blending code.
ZDoom ACS script configuration: added definitions for StrLeft, StrMid and StrRight functions.
Visplane Explorer plugin will show warning message instead of chashing if current map is not in Doom map format.
Fixed a crash when trying to undo sector creation in Visual Modes.
Fixed incorrect colors in Script Editor.
