Visual mode: fog distance calculation is now much closer to GZDoom one.
Visual mode: thing brightness calculation when a thing is affected by floor glow is now much closer to GZDoom one.
Linedef edit window, UDMF: added "Reset front/back brightness" buttons.
Sector edit window, UDMF: added "Reset ceiling/floor brightness" buttons.
Internal, Visual mode, Things mode: persistent event lines are now updated only when map objects are changed instead of doing it on every display redraw.
Internal: improved Dictionary lookup times when using map objects and textures as keys.
Internal: added "Release + Profiler" solution configuration.
Updated ZDoom_ACS.cfg (Warp).

Fixed, UDMF parser: parser failed to parse decimals stored using scientific notation (like "1E-06").
Fixed, UDMF parser: incorrect line numbers were shown when displaying errors.
Changed, UDMF parser: many error descriptions are now more detailed.
Updated ZDoom ACC to Git rev. ae5f036.

"Fixed", DECORATE parser: looks like treating missing parent class as an error was way too overwhelming to some users, so parsing is no longer aborted and a warning is added instead of an error.

Added, Visual mode, DECORATE: "RenderStyle" property is now partially supported.
Added, Visual mode, DECORATE: +BRIGHT flag is now supported.
Added, Visual mode, UDMF: "Alpha" thing property is now supported.
Added, Visual mode, UDMF: "RenderStyle" thing property is now partially supported.
Added, Visual mode, Hexen map format and UDMF: "Translucent" and "Invisible" thing flags are now supported.
Added, Game Configurations: added "alpha" and "renderstyle" Thing and Thing Category properties.
Fixed, Visual mode: blockmap was not updated when moving things using "Move Thing Left/Right/Forward/Backward" and "Move Thing to Cursor Location" actions.
DECORATE parser: added a warning when unable to find actor's parent class.
Internal: current map format can now be checked using "General.Map.UDMF", "General.Map.HEXEN" and "General.Map.DOOM" properties.
Updated documentation ("Game Configuration - Things Settings" page).

Fixed: "Open map in current wad" action was accidentally broken in R2403.

Added emergency map backup system (EMBS). When the editor crashes, it will try to export a backup copy of the map structures. When the same map is loaded again, it will ask the user if he wants to restore the map.
High-DPI: fixed many issues with incorrect controls size (Tag selector width, Comment Editor size, icons size, tabs size etc.).
Cosmetic: changed map geometry dragging undo messages to more descriptive ones.
Fixed, Textures Browser, cosmetic: "Show textures in subdirectories" checkbox should be repositioned when "Long texture names" one is invisible.
Updated ZDoom_DECORATE.cfg (added A_SetFloatSpeed + a couple of fixes).

Fixed, Visual mode, Auto-align actions: incorrect texture was used when clamping texture offsets of 3D floor sides.
Fixed, Numeric textbox: incorrect character was treated as decimal separator character was used when using certain Windows regional settings.
Changed, Edit Things window: when applicable, the "Filter" textbox is now focused when opening the window.
Changed, Sector Effects browser window: when applicable, the "Filter" textbox is now focused when opening the window.
Changed, Edit Things window: when the "Filter" textbox is focused, pressing the "Down" key will now switch focus to the Things list.
Changed, Sector Effects Browser window: when the "Filter" textbox is focused, pressing the "Down" key will now switch focus to the Effects list.
Changed, Linedef Action Browser window: when the "Filter" textbox is focused, pressing the "Down" key will now switch focus to the Actions list.
Configurations, Doom map format thing flags: changed "Multiplayer" flag name to "Multiplayer only".

Added some boilerplate to the rendering system. It's now impossible to start new rendering cycle if the previous one hasn't finished yet.
Changed: OS name, GPU name and GZDB revision info are now added to the exception text and GZCrash.log.
Fixed, cosmetic: toolstrip separators visibility must be updated when resizing the main window.
Internal: removed Plug.DisplaySize, Plug.DisplayLocationAbs and Renderer.ViewportSize. The same data can be accessed from anywhere using General.Interface.Display.Size and General.Interface.Display.LocationAbs. Also Plug.DisplayLocationAbs returned incorrect coordinates...

Changed, Drag Things mode: things position is now snapped to integers after finishing dragging. Also removed some unneeded update code.
Fixed a crash when deleting sectors (introduced in R2399).

Added, Texture Browser: added "Show textures in subdirectories" checkbox (enabled by default). When enabled, textures from current PK3/PK7/Directory resource directory and it's subdirectories will be shown. Otherwise, only textures from current directory will be shown.
Removed, Texture Browser: removed "Show image sizes" checkbox. "Show texture and flat sizes in browsers" preferences setting is now used instead.
Fixed, Things mode: event line between pre-last and the last PatrolPoint was not drawn.
Fixed, Things mode: highlight range for sizeless things (things with "fixedsize" game configuration property) was calculated incorrectly.
Fixed: fixed a crash when opening Script Editor after using "Open map in current wad" command to switch to UDMF map with SCRIPTS lump when current script configuration was not saved in the wad's .dbs file.
Fixed: map closing events were not triggered when using "Open map in current wad" command, which could potentially result in plugin crashes/incorrect behavior.
Fixed: Sector Drawing overrides panel could trigger an exception when closing the map during resource loading.
Internal: added "Debug + Profiler" solution configuration, added 2 profiling methods to DebugConsole.
Internal: rewrote MainForm.DisplayStatus() / StatusInfo to handle selection info in a more structured way.
Fixed, internal: some destructors could potentially be executed more than once potentially leading to exceptions. Other destructors were not called at all.
Updated ZDoom_DECORATE.cfg.

Fixed: map file lock check was performed in incorrect place leading to always reporting the map file as locked on Windows XP.
Fixed, DB2 bug (partially): 4 settings were reset to the state saved in the program configuration after applying the changes made in the Preferences window.
Fixed: several Brushes were not disposed in ImageBrowserItem (DB2 bug) and ColoredComboBox, resulting in a very slow memory leak.
Fixed, Linedefs Mode, cosmetic: incorrect distance was used when calculating vertex insert preview opacity.
Changed, Script Editor: disabled indentation guides.

Fixed, "Synchronize selection between Visual and Classic modes" setting: vertex selection synchronization was not working when switching from Visual to Classic mode. Also fixed a typo in the setting's name.
Fixed, StairSectorBuilder mode: settings form still used "Cancel OK" button order.

Added, Classic modes: default thing arguments are now taken into account when highlighting related map elements.
Probably fixed an exception when trying to check which program(s) lock the map file on Windows XP.
Changed: added an option to try to close all programs, which lock the map file when saving the map and the map file is locked (requires Windows Vista or newer).
Fixed, Preferences window: some trackbars had incorrect background color.
Fixed, General interface: in some cases status messages were almost immediately replaced by selection info messages.

Changed: when the editor is unable to save the map, it will now display the list of processes, which lock the map file.
Fixed, Update Checker: the existence of Updater.exe and Updater.ini was not checked when using Help -> Check for updates command.

Added: Auto-updater window now has "Ignore this revision" checkbox. If enabled, the window will show up only if a newer update is available. 
Fixed, Edit Selection mode: sector highlight was not updated when switching from Edit Selection to Sectors mode.
Fixed, Edit Selection mode, UDMF: in some cases texture scale Y was flipped when applying/canceling changes made in the mode.
Probably fixed a crash caused by uninitialized Association when highlighting map elements.
Fixed, Comments Panel plugin: selection info was not updated when selecting map elements in the side panel.
Fixed, Tag Explorer plugin: selection info was not updated when selecting map elements in the side panel.
Fixed a typo in Hexen_things.cfg.

Fixed: in some cases the number of generalized sector effects displayed in Sector info panel and action selector control was calculated incorrectly.

Fixed, Visual mode: double-sided middle texture highlighting transparency check didn't take TEXTURES scaling into account.
Fixed, long texture names: textures located in a directory/pk3/pk7 root can't have long texture names.
Fixed, texture selector controls, long texture names: both long and short texture names should be added to texture name auto-completion list. 
Changed: "Grid Increase" and "Grid Decrease" actions can now be bound to mouse wheel.

Fixed, DB2 bug: side panel's tabs were drawn incorrectly when panel's height was lower than cumulative tabs height.
Visual mode, GLOOME: wall/floor/ceiling sprites are now rendered closer to the way it's done in GLOOME.
Sectors mode, UDMF: some cosmetic tweaks to comment icons rendering.
Classic modes: linedef rendering is now skipped when it's visible length is very short.
General interface: fixed a possible crash when clicking on the warnings count label when it was updated from the background thread.

Fixed, Visual mode: texture coordinate generated to test if double-sided middle texture is transparent was shifted 1 pixel up.
Fixed, Visual mode: offsets of GLDEFS lights were not affected by thing's angle.
Updated SharpCompress (0.10.3 -> 0.11.1).
Updated ZDoom_DECORATE.cfg.

Fixed, text parsers: the parser could stuck in infinite loop when trying to skip an unclosed block comment.

Removed Trackbar.dll.

Changed, Visual mode: changed thing fog calculation logic. Should be closer to GZDoom now.
Fixed, GLDEFS parser: "height" texture parameter was not treated as optional.
Fixed, text lump parsers: in some cases incorrect line number was displayed in error and warning messages.
Fixed, Visual mode: glow effect was not applied to sectors with 3 sidedefs.
Fixed, Visual mode: in some cases glow effect was not updated when replacing textures. 
Fixed, general interface: "Full Brightness" button state was not updated during map loading.
Fixed, Drag Linedefs/Vertices/Sectors/Things modes: positions of line length labels were not updated while panning the view.
Cosmetic: added a bunch of new icons.
Cosmetic: changed Visual mode crosshair.

Changed, Drag Linedefs/Vertices/Sectors/Things modes: line length labels are now displayed the same way as in Draw modes.
Changed, Drag Linedefs/Vertices/Sectors/Things modes: "lock movement to cardinal directions" mode (Alt-Shift-Drag) now locks movement in 4 directions instead of 8 and doesn't snap map elements to nearest grid intersections when they are not aligned to it. 
Added, Visual mode, GZDoom, DECORATE: FORCEXYBILLBOARD flag is now supported.
Added, Visual mode, GLOOME, DECORATE: FLOORSPRITE, CEILSPRITE, WALLSPRITE, ROLLSPRITE and STICKTOPLANE flags are now supported (implementation is somewhat broken ATM and probably doesn't work the same way as in GLOOME, because Windows build with most these features is nowhere to be found...).
Fixed, Visual mode: in some cases Thing brightness was calculated incorrectly.
Updated ZDoom_DECORATE.cfg.

Changed, Draw Lines/Rectangle/Circle/Curve modes: line length labels are now repositioned to stay on screen when line's start or end is not visible.
Added, Map Analysis mode: added "Check map size" check. It will generate a warning when map's width or height is larger than 32767 m.u.

Changed, General interface: all main menu toolbars are now visible when starting the editor for the first time.
Changed, General interface: "Prefabs" and "Edit" menus are now hidden when no map is loaded.
Changed, General interface: moved "Dynamic Grid Size" menu item to the "Edit" menu, also moved the button to the matching position on the toolbar.
Changed, General interface: changed "Show Comments" menu item position in the "View" menu, also moved the button to the matching position on the toolbar.
Game configurations: removed "gamedetect" block, because it was unused by the editor.
Updated documentation ("Map Format Settings" page).

Classic modes: added "Dynamic grid size" option (available in the View menu and on the main toolbar). When enabled, grid size will be automatically adjusted based on current zoom level.
Updated ZDoom ACC to rev. 19995bb.
Updated ZDoom_ACS.cfg and ZDoom_DECORATE.cfg.

Changed, curved event lines, Visual mode: associated lines were not rendered as curved when the control object was not on screen [Xabis' patch #3].
Game configurations: removed "GZDoom only" from FraggleScript actions (because FraggleScript can be used in ZDoon).
Internal: fixed a couple of bugs in DebugConsole.StopTimer();

Fixed, Things mode, curved event lines: in some cases IsCurved property was not applied to all InterpolationPoints in a path.

Added, Things mode, Visual mode: event lines for InterpolationPoints are now curved when appropriate setting is enabled in the control thing (PathFollower/ActorMover/MovingCamera) [heavily inspired by Xabis' patch].
Added, Things mode: the editor will try to reconnect the path when deleting InterpolationPoints and PatrolPoints.
Internal: RenderArrows method now works the same way in Renderer2D and Renderer3D.
Internal: Line3D now has "renderarrowhead" property.

Fixed, UDMF: the implementation of "moreids" property was different from UDMF standard. This issue affected only linedefs and sectors with more than 2 tags.

Added, Things mode: target tags are now automatically assigned when duplicating (shift-dragging) PatrolPoints and InterpolationPoints.
Fixed, ThingsMode: fixed highlighted thing disappearing when using paste action while highlighting a thing.

Classic modes: added "Toggle Grid" action (default key is Alt-G), new menu item in the View menu and new toolbar button.
Changed, Things mode, cosmetic: tweaked thing sprite/bounding box appearance a bit more...
Fixed, Linedefs mode, cosmetic: fixed event lines and sector highlights flickering when view panning was started while displaying action highlight.

Changed, Things mode: things are now rendered with a bit of transparency, so things beneath other things are now visible.
Fixed, Things mode: in some cases it was impossible to highlight a thing beneath other thing when their positions were the same.
Changed, 2D modes: changed thing bounding box and arrow image.
Fixed, cosmetic, 2D modes: in some cases thing arrows were rendered bigger than thing bounding boxes.

Linedef Color Presets: completely redone Linedef Color Presets UI. Now it's done the same way as Things Filters UI.
Linedef Color Presets: Linedef Color Presets can now be disabled.
Things Filters window: a warning icon is now displayed near the filter name in the filters list when the filter has no usable settings.
Change Map in Current WAD window: keyboard focus was not set to initially selected item.
Changed the default wad filename from "unnamed.wad" to "[map name].wad".
Updated documentation ("Custom linedef colors" page).

UDMF: most of the code now supports multiple sector/linedef tags ('moreids' UDMF property). The only things left out are Tag Explorer and Tag Range plugins.

Fixed, Edit Selection mode: "High precision positioning" setting was set to false after using the mode in non-UDMF map format.

UDMF: implemented 'moreids' handling. Currently this includes the core stuff, new TagsPicker control in Edit Sector/Linedef windows and updated Sector/Linedef Info panels.

Changed, Linedef/Thing Edit windows: when using ACS specials and choosing a script with arguments, appropriate action argument names are replaced with script argument names.
Changed, Linedef/Thing Info panel: when displaying a linedef/thing with an ACS special, which uses a script with arguments, appropriate action argument names are replaced with script argument names.
Changed, Sector/Linedef/Thing Edit windows, Comments tab: window is no longer closed when pressing Enter while editing a comment. Newline is inserted instead.
Changed: Script Editor window is now toggled to normal state when pressing "Show Script Editor" button if said window was already open, but minimized.
Fixed: in some cases action arguments were not cleared during setup when displaying multiple map elements with mixed argument values.
Internal: added ArgumentsControl.