Added, Visual mode: added "Toggle Alpha-based Texture Highlighting" action. When enabled, 3d floor textures and middle textures on double-sided lines will be highlighted only when the crosshair points at a non-transparent pixel.
Changed: multi-part sectors are now better preserved after drawing new lines.
Changed, TEXTURES parser: patch loading errors are now ignored for textures with "NullTexture" option.
Changed, Game configurations: changed default door action arguments to better match vanilla ones.
Fixed, Actions: in some cases keyboard shortcuts involving Ctrl/Alt/Shift modifier keys were displayed incorrectly.
Fixed(?): probably fixed inability to save map wad in Slade 3.
Updated ZDoom_ACS.cfg.
Updated ZDoom_DECORATE.cfg.
Updated ZDoom ACC.

Changed, Classic modes: displayed mouse map position coordinates are now snapped to current grid size.
Updated model pitch handling to match current GZDoom implementation.
Fixed imprecise vertex coordinates generated by Draw Ellipse mode.
Fixed a resource loading exception when opened map file wad was located in the root of a Directory resource.
Internal: changed output of all InterpolationTools methods from int to float.
Fixed, Internal: InterpolationTools.InterpolateColor() delta usage was inverted.

Added, Edit Selection mode: Added "Adjust height" setting. It can be used to adjust floor/ceiling height of selected sectors based on the sector selection was in and the sector selection was moved into.
Removed "Adjust heights to match relatively with surrounding sector" option from Preferences -> Pasting, because sector height adjustments are now handled by Edit Selection mode.
Fixed, Sector info panel: in some cases 0 deg. floor/ceiling texture rotation was triggering texture offset/scale/rotation UI parts to be shown.
Fixed even more cases when sidedefs belonging to linedefs, which were moved on top of existing linedefs, were incorrectly reassigned when applying Edit Selection and Drag Geometry modes.
Fixed, Bridge mode: in some cases calculated floor/ceiling heights were not applied to the sectors created by the mode.
Changed, internal: changed program's CurrentCulture to InvariantCulture.

Fixed, Visual mode: texture offsets were updated multiple times when moving texture offsets of several extrafloor sides linked to the same control sidedef.
Fixed, Visual mode: sidedef geometry of sectors affected by "Copy Slope" effect was not updated when the source slope was modified.

Added, Sound Environments mode: sound environments of the same type are now colored using the same color.
Added, Sound Environments mode: current sound environment is now highlighted (can be toggled using "Toggle Highlight" action).
Added: Tag selectors now have up/down buttons.
Fixed, Sound Environments mode: sound environments were not updated after performing Undo/Redo actions.
Fixed, Sound Propagation mode: sound zones were not updated after performing Undo/Redo actions.
Internal: moved "Toggle Highlight" action to the core, also changed it's category to "View".
Internal: "Toggle Highlight" action state is now saved in the Program configuration.
Updated ZDoom_DECORATE.cfg (GetZAt).
Updated ZDoom_linedefs.cfg (Sector_SetPortal args).

Changed, Visual mode: "Auto-align textures" and "Paste Textures Floodfill" actions now use visual mode geometry to determine whether a sidedef part should be processed. This fixes inability to apply said actions to sidedef parts only visible because of slopes.
Fixed, Visual mode: both "With same texture" and "With same height" Select modifiers are now checked when both of them are used at once (previously a sidedef part/floor/ceiling was selected when any of those matched).

Fixed, Linedefs mode: fixed inability to highlight linedefs when "Stitch geometry within" setting was set to 0.
Fixed, Visual mode: fixed a crash when performing "Auto-align textures" actions on selected sidedefs when there were also floors/ceilings selected.

Fixed, Visual mode: rendering effects of "Slope floor/ceiling to here" things (9500/9501) should not be applied when their arg0 is 0.

Fixed, Visual mode: "Rotate CW"/"Rotate CCW" actions should update thing-based effects when used on Things.
Added/restored, Visual mode: restored "Move Texture Left/Right/Up/Down by 8" actions, added "Move Texture Left/Right/Up/Down by Grid Size" actions (default keys are Ctrl+arrow keys).
Fixed, Game configurations: Hexen's Bell actor was missing "hangs" flag.

Added: holding Control key while switching to/from Visual mode will now temporarily disable position synchronization (works only when 'Synchronize camera position between 2D and 3D modes' Preferences option is enabled).
Fixed severe lock-up after finishing dragging many vertices/linedefs/sectors in Classic modes.
Updated documentation ("Synchronizing camera position").

Fixed, Visual mode: in some cases translucency was ignored on inner top sides of translucent 3d floors.
Internal, Script Editor: moved some setup/auto-completion logic to separate classes.
Updated ZDoom_DECORATE.cfg (A_QuakeEx).

Fixed, Visual mode: 3d floor outer sides were not updated after toggling rendering effects off, then on.
Updated ZDoom_DECORATE.cfg (GetAngle function). 

Fixed, Visual mode, UDMF: in some cases Fade color was not applied to floor and ceiling surfaces of 3d floors.
Fixed, Visual mode: in some cases not all sidedef geometry was updated when updating sectors with Plane Align (181) action. Also fixed some more unnecessary geometry updates.
Fixed, Linedefs mode, Things mode: in some cases deleting linedefs/things caused a crash when trying to update text labels.
Fixed, Draw Lines mode: in some cases the drawing was prematurely finished when "Auto-finish drawing" option was enabled.

Added, Visual mode: "Increase/Decrease Scale", "Reset Texture Offsets" and "Reset Local Texture Offsets" actions now work when used on 3d floor sides.
Fixed: CVARINFO parser was unable to parse negative int/float values.
Fixed: in some cases TextLabel text size was checked before it was calculated. 
Internal, Visual mode: reduced the number of unnecessary geometry updates when changing map geometry.
Updated ZDoom_DECORATE.cfg (atan2 and VectorAngle).

Updated ZDoom_DECORATE.cfg.

Fixed, Visual mode: in some cases "Flood-fill textures" actions were not working when "use long texture names" Map Options setting was enabled.

Fixed, Things mode: in some cases selection labels were not updated after editing a thing.
Fixed, Things mode: selection labels were positioned incorrectly on things with FixedSize setting.
Fixed, Sectors mode: fixed a crash when selecting self-referencing sector when selection labels were enabled.
Fixed, Visual mode: in some cases Auto-align texture actions were not working when "use long texture names" Map Options setting was enabled.
Fixed, MD2/MD3 loader: available animation frames upper bound check was performed incorrectly, which would cause a crash in some very special cases.
Fixed, Game configurations: most Hexen/ZDoom teleport actions use TeleportDests as teleport targets, not MapSpots.

Added, Preferences -> Appearance: added "Anisotropic filtering" and "Edge Antialiasing" settings. Also regrouped some settings.
Added, "Check polyobjects" error check: added a check for matching Polyobject and Mirror Polyobject numbers of Polyobj_StartLine action.
Changed, Visual mode: anisotropic filtering is now always applied (previously it was applied only when bilinear filtering was enabled).
Fixed, Visual mode: in some cases light values were incorrectly transferred between 3d floors and regular floors/ceilings.
Fixed, ACS parser: includes for each library must be stored separately (fixes inability to compile a script with an included library, which in turn includes files already included by the script).

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).

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

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

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, 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, 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, DB2 bug, Visual mode: in some cases (sidedef's sector ceiling lower than other side's sector floor) higher/lower sidedef picking was behaving incorrectly.

Fixed, Visual mode: sector geometry was not updated after changing sector brightness under a 3D floor.

Fixed, Texture Browser window: in some cases navigating the textures list using up/down arrows caused an exception.
Fixed, Map Analysis window: fixed an exception on copying warnings to clipboard when the clipboard was used by other application.
Fixed, TEXTURES parser: added special handling for "TNT1A0" sprite name so a texture with this sprite as a single patch is no longer treated as failed loading.
Fixed, Visual mode: in some cases (like line slopes used in several adjacent sectors) sector effect updates were triggered multiple times for the same sector, resulting in noticeable slowdowns and in some cases in infinite recursion.
Updated ZDoom ACC.

Added, Visual mode: "Raise/Lower Floor/Ceiling to adjacent Sector" actions now take surrounding 3d floors into account.
Added, Visual mode: highlight/selection based on texture alpha now works on 3d floors.
Changed, Game configurations, TranslucentLine:208 action: renamed the second argument from "Translucency Amount" to "Opacity".
Internal, documentation: updated udmf_zdoom.txt.

Fixed, Visual mode: in some cases ceiling glow effect was interfering with Transfer Brightness effect resulting in incorrectly lit sidedef geometry.
Fixed, Visual mode: UDMF sidedef brightness should be ignored when a wall section is affected by Transfer Brightness effect.
Fixed, Visual mode: any custom fog should be rendered regardless of sector brightness. 
Fixed, Visual mode: "fogdensity" and "outsidefogdensity" MAPINFO values were processed incorrectly.
Fixed, Visual mode: in some cases Things were rendered twice during a render pass.
Fixed, Visual mode: floor glow effect should affect thing brightness only when applied to floor of the sector thing is in.
Fixed, TEXTURES parser: TEXTURES group was named incorrectly in the Textures Browser window when parsed from a WAD file.
Fixed, MAPINFO, GLDEFS, DECORATE parsers: "//$GZDB_SKIP" special comment was processed incorrectly.
Fixed, MAPINFO parser: "fogdensity" and "outsidefogdensity" properties are now initialized using GZDoom default value (255) instead of 0.

Fixed, Visual mode: fixed inability to drag auto-selected sidedef parts using mouse when "Synchronize selection between Visual and Classic modes" setting was enabled.
Fixed, Visual mode: fixed incorrect auto-selected sidedefs texture offset clamping when "Synchronize selection between Visual and Classic modes" setting was enabled.

Updated skybox model to better match GZDoom's skybox. Also the sky texture was flipped horizontally.
Fixed, Visual mode: "Select with the same texture" action is now able to select sidedef parts only visible because of slopes.
Fixed, Visual mode: skybox texture was not updated after using "Open map in current wad" action.
Fixed, Visual mode: in some cases Visual camera was placed below sector's floor when "Sync camera position between 2D and 3D modes" setting was enabled.
Fixed: numeric thing flags with inverted UDMF flag defined in "thingflagstranslation" Game configuration block were lost when copy-pasting a thing.
Fixed, command line arguments: fixed a crash when loading a map from a wad with existing .dbs file.