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)".

Map Analysis mode: fixed a couple of minor glitches related to enabling/disabling results list, "fix" buttons and "fix all" checkbox.

Updated documentation.

Map Analysis mode: results list now has a context menu, which allows to hide/show results based on type of selected result and to  copy description of selected result to clipboard.

Map Analysis mode: export to file command will now show "Save File" dialog instead of putting the file in the same folder as the map, also added some boilerplate.
Tag Explorer plugin: save to file command will now show "Save File" dialog instead of putting the file in the same folder as the map, also added some boilerplate.
Internal: reformatted GZCrash.log a bit.

Comments Panel: probably fixed a possible crash when UpdateList() is triggered during map unloading.

Map Options Form: example map name now uses current game's naming scheme.

Texture Browser Form: some minor logic fixes (no texture groups were selected when initial texture was empty and no texture group was stored in the program configuration).
Texture Browser Form: don't save current texture group when the form was canceled.
Keyboard Shortcut Reference export: generated html will now be saved to program configuration folder if working folder is write-protected.
Internal: added SupportedMapFormats property to EditModeAttribute. A mode with this property specified will be available only in specified map formats.
Interface: Ceiling Align Mode and Floor Align Mode are now enabled by default.
Interface: Ceiling Align Mode and Floor Align Mode are now only available in UDMF map format.
Interface: Visplane Explorer Mode is now available only in Doom map format.

Find & Replace Mode: sector effects and linedef actions are now searched on bit by bit basis. That means map elements with partially matching Generalized effect/action can now be found.

Internal, Edit Sectors form: more changes to "Slopes" tab logic. It's still incomplete...

Import .obj as Terrain: created terrain was horizontally flipped when importing a model with up axis set to X or Z.
Also, I would like to use this opportunity to thank Siberian Tiger from DTD Team for helping me with SVN builds for more than two years. You made my constant wrestling with the code a much less tedious process.

Import .obj as Terrain: vertex order was incorrect when creating sectors from a model with up axis set to Z.

Classic modes: Draw Grid, Rectangle and Ellipse modes were missing "toggle grid snapping" mode (enabled by holding Shift key while drawing).

Game Configurations: changed default map name for Doom maps to "E1M1".
New Map Form: "E1M1" is now used as a default name for Doom maps.
Thing Browser Control: double-click event is now sent only if user clicked in the node's label area.
Interface: added info messages for several toolbar toggles.
Interface: made Brightness icon more readable when using dark windows themes.

Visual mode, UDMF: added some boilerplate to prevent invalid sector slopes from showing up/crashing the editor. 

Fixed: MapSet.GetSectorByCoordinates() returned "false" in some cases when a given coordinate was on top of sector's vertex.
Internal: UDMF sector slopes and offsets are no longer stored in sector.Fields. Use sector.FloorSlope, sector.FloorSlopeOffset, sector.CeilingSlope and sector.CeilingSlopeOffset.

Visual mode, 3d floors: fixed broken 3d floor visibility detection (which failed in some cases when real floor or ceiling was sloped).

Tag Range plugin: tags can be set in relative mode (when this mode is enabled, generated values are added to existing tags instead of replacing them).
Updated documentation.

Map Analysis form is now resize-able.
Map Analysis form: number of found errors is now shown in the form's title.

Fixed a typo in the Preferences form.

Sectors mode: things inside of selected sectors can be moved when dragging sectors. This behavior can be toggled by the new button on Sectors mode's toolbar.
Sectors mode: changed Alt-key handling. Now it only enables "snap to grid increment" mode.
Things mode: "snap to grid increment" mode now works in this mode.
Updated documentation.

Visual mode: some parts of 3d floor were shown even when it was above real ceiling/below real floor.
Visual mode: real floor was colored by 3d floor's color even when it was below real floor.
Action Browser form: keyboard focus is now set to Filter text box by default.

Visual mode: unrelated sidedefs were selected when trying to select empty texture using "Select with the same textures" action.

Classic modes: you can now hold ALT key while dragging map items to lock movement to grid increments relative to initial position.

Linedefs Mode: "Flip Linedefs" action now tries to align linedefs, so their front (or back) point towards the same sector.
Sectors Mode: "Flip Linedefs" action is now available form this mode, and it will also try to align linedefs, so their front (or back) point towards the same sector.

Draw Rectangle mode, Draw Ellipse mode: fixed a possible crash when restoring bevel/subdivisions values.
Draw Curve mode: added "Reset" button to the toolbar.
Draw Rectangle/Ellipse/Grid modes: "Reset" toolbar buttons didn't have a proper tooltip.

Map Analysis mode: "Check overlapping vertices" was setting incorrect total progress value, which could cause a crash in some cases.

Visual mode: middle sidedef geometry of single-sided linedefs was rendered differently than in (G)ZDoom in some cases.