Fixed, Visual mode: alpha-based texture picking didn't work correctly on HiRes images.
Fixed, Visual mode: fog density was calculated incorrectly for things lit by dynamic lights.
Fixed, Edit Sector window, UDMF: "Fade" and "Light" color pickers initial values were incorrect when displaying mixed values.
Fixed, Edit Thing window, UDMF: "Color" color picker initial value was incorrect when displaying mixed values.

Changed, Draw Lines and Draw Curve modes: "Auto-finish drawing" option now works regardless of "Continuous drawing" option (previously it worked only when the latter was enabled). 
Changed: position and size of the "Errors and Warnings" window is now stored while the editor is running.
Internal: rewritten parts of long texture names support code. It now involves much less special handling.
Updated ZDoom_DECORATE.cfg (A_QuakeEx, A_CheckBlock).
Updated ZDoom_ACS.cfg (QuakeEx).
Updated ZDoom ACC (QuakeEx).

Fixed: HiRes images should be loaded from subdirectories too.
Fixed: in some cases the editor was unable to locate existing "LoRes" images when loading HiRes images.
Disabled some HiRes-related warnings, because the editor doesn't track all sprites or graphics.

Added "Sidedef Lower Texture", "Sidedef Middle Texture" and "Sidedef Upper Texture" Find and Replace modes.

Fixed, Game configurations: some Generic_Floor:200 and Generic_Ceiling:201 parameters were named incorrectly.

Changed, Select Similar Sectors action: when "Effect" option is enabled, all sectors with at least one matching generalized/predefined effect will be selected.
Added, Tag Explorer plugin: a separate category for each generalized/predefined effect is now created when "Sort by action special" sort mode is used.
Added, Edit Effect window: normal and generalized effects can now be set at the same time.
Fixed, Edit Action window: in some cases Generalized actions were incorrectly processed.
Fixed, Edit Effect window: in some cases Generalized effects were incorrectly processed.
Fixed, Select Similar window: Tab control was incorrectly anchored.
Fixed, Nodes Viewer mode, cosmetic: segs angles were calculated incorrectly when showing nodes in classic format.
Fixed: HiRes textures, which didn't override any texture or flat were not loaded. 
Fixed, Tag Explorer plugin: linedef action categories were missing title when "Sort by action special" sort mode was used.
Cosmetic: renamed "Grid Setup" action to "Grid and Backdrop Setup".

Internal: removed some duplicate casts, marked some classes is IDisposable, some streams were disposed more than once.

A warning is now displayed when map uses more than one official IWAD as a resource.

Map saving: map lumps position in the wad is now kept persistent when saving it (previously / in DB2 map lumps were always pushed to the end of the wad when saving it). 
Internal: added NeutralResourcesLanguageAttribute to all assemblies. Theoretically this should result in a bit better performance when accessing embedded resources.
Updated ZDoom_DECORATE.cfg (A_Chase flags).

TEXTURES support: both patch Blend syntaxes are now supported (previously only "Blend <string color>[,<float alpha>]" was supported).
Added X11R6RGB parser.
Rewritten parts of unhandled exceptions handling to reduce the chance of additional exceptions happening after the first one.

Game configurations: added 2 secret Sector_Set3dFloor flags. Shhh! Don't tell anybody!

Fixed source window freezing while Open Map window was open when opening a wad by dragging & dropping it on the editor's main window.
Image loading-related warnings and errors now display more information about the image resource.

Fixed, Script Editor: in some cases "[EP]" (Entry Position) markers were processed incorrectly when inserting a snippet.
Updated SharpCompress library to 0.11.5.
Updated ScintillaNET library to 3.6.3.

Added, Draw Ellipse mode: angle setting can now be changed using "Rotate Clockwise" and "Rotate Counterclockwise" actions.
Added, Draw Line and Draw Curve modes: added "Auto-finish drawing" setting. When enabled, the modes will automatically finish drawing when currently drawn lines and already existing level geometry form a closed shape.
Changed: sector-wise linedef flipping is now done using the new "Align Linedefs" action. "Flip Linedefs" action works the same as in DB2 again.
Changed: when a map was already loaded, using "Open Map" action will use that map's directory as the starting directory.
Changed: official IWADs can no longer be saved.
Changed: disabled lump ranges/duplicate entries checks for official IWADs.
Changed: wad type is now preserved when saving a map (previously all wads were saved as PWADs).
Changed: moved Updater.exe launch much closer to the editor termination point to avoid any chance of it closing the editor before it properly closes itself.
Updated ZDoom_DECORATE.cfg (A_Blast).
Updated documentation.

Changed, cosmetic: elapsed time is now displayed after resources loading finishes.
Changed, internal: changed Clock.CurrentTime type to long.
Fixed, Tag Statistics window: in some cases the map view was not updated after selecting items in Sectors/Linedefs/Things columns. 
Fixed, cosmetic: Draw Curve mode icon was missing a shadow.

Fixed, Map Analysis mode: fixed a crash when running "Check Polyobjects" check on a map without lines using "Polyobj_StartLine" action.
Updated ZDoom_linedefs.cfg (Line_SetPortalTarget).
Updated ZDoom_ACS.cfg (Line_SetPortalTarget).

Changed, Game configurations: "Polyobject Anchor" things should not trigger "Thing outside the map geometry" error in the Map Analysis mode.
Updated ZDoom_DECORATE.cfg (A_SetScale).

Added, Visual mode: both Sky1 and Sky2 MAPINFO properties are now used when creating classic skybox texture.

Fixed, ACS parser: the names of include files bundled with acc compiler should be also checked for duplicate includes from user scripts, unless those user scripts are libraries.

Fixed, Visual mode: in some cases GLDEFS glow effect was not updated after changing floor/ceiling texture.
Fixed, Draw Rectangle and Draw Ellipse modes: in some cases pressing "Reset" button did not update the shape preview.
Fixed, DB2 bug: sector geometry was not updated after undoing "Flip Sidedefs" action.

Fixed, Game configurations: Point Pusher (5001) and Point Puller (5002) things were missing from Boom configs.

Fixed, ACS parser: the names of include files bundled with acc compiler should be also checked for duplicate includes from user scripts.
Fixed, Script Editor: fixed another case when clicking a script error item didn't open/switch to the error source file.
Fixed, Update checker: fixed a crash when trying to check for update without active Internet connection.

Changed, Draw Ellipse mode: lowered minimum subdivisions to 3.
Fixed, Browse Action and Browse Effect windows: first option was always selected for any generalized action/effect parameter during generalized action/effect setup.

Changed, Draw Ellipse mode: Increase/Decrease bevel actions now always increase (and decrease) to the next even number.
Changed, Test Map drop-down: warning icon is now displayed when associated test engine executable can not be located, question icon is now displayed when the editor is unable to get the icon from the associated test engine executable.

Added, Draw Grid mode: "Lock slices to grid" now operates in 4 modes: "None", "Horizontal", "Vertical" and "Both". Can be helpful when drawing ladders and such.
Changed, all drawing modes: changeable drawing mode settings are now persistent.
Changed: "Dynamic grid size" mode is now disabled when changing grid size manually.
Documentation: "Command Line Parameters" topic contained a lot of incorrect information...
Updated ZDoom_DECORATE.cfg.

Fixed, Script Editor: fixed a crash when trying to open Script Editor in a Doom map format map.

Fixed, Custom Fields UI: in some cases mixed user var values were displayed incorrectly.

Fixed, Edit Linedefs window: textures on selected sidedefs must be updated when toggling "Replace unused textures" setting.
Fixed, Texture Selector control: in some cases actual textures were never loaded/displayed when "Replace unused textures" setting was disabled.
Fixed, Script Editor: auto-completion list is no longed displayed when editing comments, includes or strings.

Fixed, Edit Things window: thing type validation when editing multiple thing types was broken in r2527.

Fixed, DECORATE parser: quoted actor string properties (like RenderStyle) were processed incorrectly.
Fixed(?), Update checker: in some cases incorrect update check result was displayed.

Added, Linedef Edit window: added "Replace unused textures" checkbox. When disabled, textures on unused sidedef parts won't be replaced when changing textures. For example, you can now replace sidedef textures of the whole map at once without assigning middle textures to all double-sided sidedefs.
Updated documentation ("Compiling GZDoom Builder" - added "Quick start guide" section).
Updated ZDoom_DECORATE.cfg.

+A couple of cosmetic tweaks and fixes.
Updated ZDoom_DECORATE.cfg.

Fixed, Visual mode: fixed a crash, which happened after these steps: delete things in Classic mode -> undo things deletion in Visual mode -> redo things deletion in Visual mode.

Fixed: checking read-only flag of non-existing files is not a good idea... (fixes a bug introduced in r2520).
Updated ZDoom_DECORATE.cfg (min/max).
Documentation: fixed cosmetic formatting issues in "DECORATE keys" page.

Changed, Action arguments control: arguments are no longer reset to default values when changing action/thing type when old and new argument types and names are the same.