Import Wavefront .obj as Terrain mode: floor height of each created sector is now set to the average height of an .obj polygon it was created from.
Import Wavefront .obj as Terrain Settings window: added "Use slopes" checkbox. When enabled, the mode will create slopes using vertex height offsets (UDMF) or Floor Vertex Height things (1504).
Fixed, Visual Mode: things were rendered at wrong height after using "Lower/Raise Height" actions in sectors with sloped floor (or ceiling for ceiling-aligned things) 
Fixed: info panel was not updated after switching to another Edit Mode.

Script Editor: expanding snippet by pressing the Tab key now works only when the text cursor is at the end of a keyword.
Updated ZDoom ACC.
Updated ZDoom_things.cfg.
Updated documentation.

Fixed, Texture Browser Form: well, I broke "Tab" key functionality again (in previous commit)...
Maintenance: changed curly braces style to match DB2 one (hopefully not breaking anything in the process...).
Maintenance: changed private method names casing to match DB2 one.

Added long texture names support (enabled when "longtexturenames" game configuration property is set to true and "Use long texture names" check box is checked in Map Options).
Open Map in Current WAD: resources are now reloaded when current and target map's resources don't match.
Added some boilerplate to UniversalParser and PK3FileImage.
Internal: ImageSelectorControl now has "UsePreviews" property.
Internal: added ConfigurablePictureBox.
Updated ZDoom_DECORATE.cfg.

Internal: removed some unrelated stuff from NodesViewer.csproj.

Changed: thing sprite is now displayed in ThingBrowserControl.

"Find Any Texture or Flat", "Find Sector Flat" and "Find Sidedef Texture" options now support "*" (match any number of characters) and "?" (match any single character) wildcards.
"Find Any Texture or Flat" is now available any game configuration (previously it was disabled when "MixTexturesFlats" game configuration option was disabled, now only "Replace" functionality is disabled).
"Find Thing Flags" and "Find Linedef Flags" can now replace flags.
Added "Find Sidedef Flags" and "Find Sector Flags" search options.

Fixed, Draw Grid mode: fixed a crash on accepting the mode when start and end points had the same coordinates.
Fixed, Draw Grid mode: grid triangles are now aligned properly with previously drawn triangulated grids when using the same map grid size and "Lock slices to grid" and "Triangulate" options are enabled.
Fixed, Draw Grid mode: not all grid cells were drawn in some cases.
Fixed, Draw Grid mode: current grid size was not increased when "Lock slices to grid" was enabled and the start point was no longer on the map grid.
Changed, Draw Grid mode: snap to grid is now always enabled and snap to nearest is now always disabled when "Lock slices to grid" is enabled.
Changed, Draw Grid mode: when grid's width or height is 0 when accepting the mode, a segmented line is now drawn instead of just a line.

Fixed: in some cases selection synchronization logic worked incorrectly when switching from Visual to Classic mode.

Randomize Sectors form: floor/ceiling height controls now have "Offset mode" drop-downs. Available modes are "Raise and lower" (default), "Raise only" and "Lower only".
Consistency, Randomize Sectors form: persistent settings are now saved only when applying changes done in the form (e.g. in the same conditions as in Randomize Things / Vertices forms). 

Fixed: Randomize Sectors, UDMF: vertex height changes were not undone properly after using the mode (I broke it in r2101).
Fixed: Randomize Sectors: floor/ceiling textures can not be used as lower/upper textures when "MixTexturesAndFlats" is disabled. In this case the corresponding option is now changed to "Use default texture".

Randomize Sectors form: added "Use vertex heights" check-boxes. When enabled and used on triangular sectors, it can be used to create a terrain-like look.
Updated ZDoom_DECORATE.cfg.
Updated documentation, rearranged contents a bit.

Fixed, WavefrontExporter: floor and ceiling textures were not exported when using "classic" game configurations (ones with disabled "MixTexturesAndFlats" option). This should also fix incorrect flats on exported model when there are flats and textures with the same name.
Fixed, WavefrontExporter: 3d floors geometry and wall geometry around them was created incorrectly.
Fixed, WavefrontExporter: floor and ceiling textures of non-Vavoom 3d floors were swapped on exported geometry.

Fixed incorrect non-UDMF <-> UDMF skills translations in Strife_misc.cfg.

Renamed "Save Screenshot (editing area only)" action to "Save Screenshot (active window)". It will now save a screenshot of currently active window, or editing area if no windows are open.
Added icons for "Save Screenshot" menu items.
Development: "Save Screenshot (active window)" action will work on a child Form only if it is inherited from DelayedForm.

General interface: dynamic lights rendering mode and model rendering mode are now selected via drop-downs.
Renamed "Toggle dynamic lights rendering" action to "Show dynamic lights".
Changed: "Show dynamic lights" action now toggles between available dynamic light rendering modes.
Renamed "Toggle models rendering" action to "Show models".
Changed: "Show models" action now toggles between available model rendering modes.
Removed "Toggle dynamic lights animation" and "Render selected/all models" actions.
Fixed, Randomize Sectors form: selection highlight was not updated after applying the changes when the form was shown in Sectors mode.
Consistency: selection is now cleared after applying changes done in Randomize Things and Randomize Vertices forms.
Fixed, Classic modes: sprites of things with attached models were not rendered when model rendering was disabled.
Updated documentation.

Changed FormBorderStyle from FixedToolWindow to FixedDialog. GZDB should no longer disappear from the alt-tab list when a child form is opened.

Visual mode: "Lower/Raise Floor/Ceiling" actions now work on surfaces with sector slopes.
Cosmetic: numeric textboxes, which support relative values, now have differently colored text and a tooltip.
Internal: renamed Sector.CeilingSlopeOffset to Sector.CeilSlopeOffset, Sector.CeilingSlope to Sector.CeilSlope to match their names with similar sector properties.

Internal: added General.Interface.ActiveDockerTabName property.

Fixed: VirtualSectorField was cleared from sector properties when pasting map geometry in Doom/Hexen map formats leading to incorrect sector assignment [I broke this in r2009, so it seems].

Fixed, Classic modes: Alt-dragging map elements (e.g. "snap to grid increment while dragging" mode) was not working properly.

Map Analysis, internal: some ErrorCheckers and ErrorResult had inconsistent namespaces.
Thing Edit forms, internal: optimized missing flags check a bit.

Thing Edit Form: a warning is now displayed when a thing doesn't have any skill or class or game mode flags.
Game Configurations: moved "thingflagscompare" from Game to Map format blocks. "Check stuck things" check now works properly in Doom/Boom game configurations.
Map Analysis: fixed a possible crash during "Check texture alignment" check.
Map Analysis: ResultStuckThingInLine now highlights both thing and line.
Map Analysis: ResultStuckThingInThing now highlights both things and allows to delete any of them.
Internal, Map Analysis: rewritten parts of "Check stuck things" class.
Internal, Map Analysis: changed the way processed stuff is stored in "Check texture alignment" class.
Internal: changed CurrentDomainOnUnhandledException, so ExceptionDialog with proper info shows up even if adding exception to the Event Log failed.
Internal: changed format, in which thingflagscompare info is stored.

Fixed incorrect syntax in ZDoom_DECORATE.cfg.

Map Analysis form: fixed a crash caused by running analysis, opening another map then trying to run analysis again.
Map Analysis form: error checks are now alphabetically sorted.
Map Analysis form: added "Toggle All" check box.
Internal: CheckboxArrayControl now has Sort() method.
More fixes in ZDoom_DECORATE.cfg

Added: Map Analysis: added "Check texture alignment" check. Currently it works only in Doom/Hexen map formats.

Fixed: Drag Geometry Mode: dragged sectors, linedefs or vertices were snapped to 0, 0 in some cases when trying to snap them to a linedef fully inside of a grid cell.

Fixed: Visual mode: "Select" action with "with the same textures" / "with the same height" modifiers (Shift/Ctrl + LMB) was not working properly when used on vavoom-type 3d floor sidedefs.
Fixed: Visual mode, UDMF, "Auto-align textures" actions: vertical texture offset was calculated incorrectly for vavoom-type 3d floors.

Visual mode: "Select" action with "with the same textures" / "with the same height" modifiers (Shift/Ctrl + LMB) now works properly with vavoom-type 3d floors.

Visual mode: "Select" action with "with the same textures" / "with the same height" modifiers (Shift/Ctrl + LMB) now works when used on floors and ceilings of a 3d floor.

Sector slopes were not copied by "Copy Properties" actions and were missing from Paste Properties Options form.
Added several missing flags to ZDoom_DECORATE.cfg.

Visual mode: "Select" action with "with the same textures" / "with the same height" modifiers (Shift/Ctrl + LMB) now works when used on sides of a 3d floor.
Visual mode: "Select" action with "with the same textures" modifier (Shift + LMB) now selects adjacent sidedefs only when their height intersects with the height of the current sidedef.
Visual mode: "Select" action with "with the same textures" modifier (Shift + LMB) was not selecting connected one-sided sidedefs when used on a sidedef without a texture.
Cosmetic: fixed a couple of action descriptions in BuilderModes' Actions.cfg.
Cosmetic: MainForm.UpdateToolStripSeparators was working incorrectly in some cases.
Cosmetic: ErrorChecksForm's title was not updated when no errors were found.

The editor will fail more gracefully when no D3D device is detected.
In some cases the editor was constantly checking D3D device availability when minimized.
Added more DX-related debug output (only in Debug builds). 

Preferences: added "Vertex scale (3D)" preference, renamed "Vertex scale factor" to "Vertex scale (2D)".