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.

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

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.

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: 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.

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). 

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.

A r1959 change in ImageSelectorControl prevented inherited classes from showing properly in Visual Studio's designer.
Also made a bunch of methods static.

Sectors, Linedefs, Things, Vertices modes: added "Select Similar" action (available in <Mode name> -> "Select Similar..." menu), which lets you select map elements similar to currently selected ones, based on a set of settings.
Some cosmetic fixes in "Filter Selected Things" and "Paste Properties Options" panels.

Thing Edit Form, UDMF: added controls for setting pitch, roll, scale, render style, fill color, alpha, health and score.
Visual mode, UDMF: UDMF scale is now applied when rendering sprites.
Added Thing Statistics form (Edit -> View Thing Types...), which shows all loaded thing types with some additional info.
Visual mode: sprites with negative ScaleX and positive ScaleY were not rendered properly.
Classic modes: display was not updated after loading a sprite.
Current testing engine change was not saved on closing the program when no other game configuration settings were changed.

Added "Paste Properties Options" form, which lets you pick properties for 'Copy Properties' and 'Paste Properties' actions.
Removed CopyPasteSectorProperties plugin, because built-in "Copy/Paste Properties" actions do the same job, but better.

"Rotate Clockwise" and "Rotate Counterclockwise" actions now work in Things mode (they will rotate things) and in Sectors mode (they will rotate floor/ceiling textures based on current view mode).
Moved "Rotate Clockwise" and "Rotate Counterclockwise" actions to "Edit" category.
Tag Statistics form: help label was incorrectly aligned.
Some actions in Sectors and Linedefs modes were not used on highlighted map elements.
Some actions in Sectors and Linedefs modes created undo groups incorrectly when used on highlighted map elements.

"Preferences -> Editing -> When splitting a linedef" setting is now always used when splitting linedefs.
"Preferences -> Editing -> When splitting a linedef": added "Reset X and Y" option.
"Preferences -> Editing -> Auto-align textures of newly created linedefs" option now works in a more intelligent fashion.

Linedef Edit Form, Sector Edit Form: when several map elements with different textures are selected, the "texture stack" icon is shown in the texture selectors instead of the "missing texture" icon.
Error Checker mode: added "Check missing flats" check.
Error Checker mode: fixed several descriptions. 
Sprite patches for sprites defined in TEXTURES are now loaded from Sprites namespace.
Some of my older texture alignment code didn't work properly when strict texture/flat handling ("mixtextureflats" game configuration flag set to false) was enabled.
Fixed some incorrect checks for missing texture ("-").

According to dotnetperls.com, "new Dictionary<string, [anything]>(StringComparer.Ordinal)" works 17% faster than "new Dictionary<string, [anything]>()", so let's stick that everywhere and see what happens :)
Draw Curve Mode: added settings panel.
Sectors mode: added "Make Door" button to the toolbar.
Swapped Side panel and Info panel z-order. 
Interface: split toolbar into 3 separate toolbars. All toolbar buttons are now viewable at 1024x768.
Interface: grouped stuff in "Modes" menu a bit better.
Interface: added "Draw [stuff]" buttons to modes toolbar.
Interface: reorganized main menu. Hope it makes more sense now.
API: added General.Interface.AddModesButton() and General.Interface.AddModesMenu(), which can be used to add buttons to specific group in "Modes" toolbar and menu items to specific group in "Modes" menu, so actions, which behave like an editing mode, but are not part of one can be added there.

Draw Settings panel: added "All" buttons to "Fill Selection with Textures" and "Remove Textures form Selection" groups
Export to .obj: fixed a crash when trying to export an unsaved map.
Texture preview are now created ~25% faster.

Hints and Draw Settings panels were not removed during map closing/switching, which resulted in duplicate panels.
The way things were rendered during dragging is now used by default in Things mode.

When Draw Rectangle or Draw Ellipse mode is enabled, it's settings are now shown in side panel.
Draw Ellipse mode: increased maximum number of sides to 512.
Changed the way tags are shown in Tag Selector controls. Tags without labels are now shown as a number (not "Tag N"), and tags with label are now shown as "N (label)", not "label (N)".
Tag labels are now shown in Thing, Sector and Linedef info panels.
Once again changed the way things are rendered while dragged.
Rearranged the label in PairedIntControl and PairedFieldControl (it is now behind numeric controls).
Optimized MapSet.GetSectorByCoordinates().

Increased performance when deleting things in Things mode, linedefs in Linedefs mode and sectors in Sectors mode.
Increased performance when canceling Edit mode after pasting.
"Export to Wavefront .obj" function: current selection is now converted to sectors before running the function (previously it would export selected sectors when there were sectors selected, or the whole map when no sectors were selected).

Visual mode: changed "Move Texture Left/Right/Up/Down by 8" actions to "Move Texture Left/Right/Up/Down by cur. grid size"
Visual mode: holding Ctrl-Shift while dragging texture with the mouse will snap texture offsets to current grid size.
Classic modes: interiors of highlighted sectors are now highlighted when the action target of currently highlighted map element is sector.
Unhandeled exceptions infos are now written to the event log.

Added Draw Settings side panel, which replaces Set Default Textures Form and allows to set textures, brightness and floor/ceiling heights to use when drawing sectors. Used settings are now saved in the map's .dbs file.
Location and active tab of all Edit Forms are now stored while GZDB is running.
Focus management between editing window and the rest of the interface should work better now.
Tag Explorer plugin: editing window was not updated properly when Edit forms were opened from Tag Explorer.
Tag Explorer plugin, UDMF: comment editing was incorrectly initialized in some cases.

Sectors mode: effect and tag overlay can now be toggled separately from selection numbers.
Sectors mode: "View Tags and Effects" and "View Selection Numbering" settings are now saved to program configuration.
Sectors mode: removed "Lower Floor by 8 mp", "Raise Floor by 8 mp", "Lower Ceiling by 8 mp" and "Raise Ceiling by 8 mp" actions.
"Increase Brightness by 8" and "Decrease Brightness by 8" actions now work in Sectors mode.
Moved "Increase Brightness by 8" and "Decrease Brightness by 8" actions to "Edit" category. 
"Toggle Highlight" action now works in Sectors mode.
Moved "Toggle Highlight" action to "Tools" category.
Removed Brightness mode.
Updated documentation.

Visual mode: added support for "fogdensity" and "outsidefogdensity" MAPINFO properties.
Sector Info panel now shows the number of sector's sidedefs as well as light and fade colors (UDMF only).
UDMF: Sector and sidedef flags are now copied/pasted when using "Copy Properties" and "Paste Properties" actions.
Fixed: in some cases default texture overrides were used even when corresponding option was disabled.
Sector Edit form: light and fade values were not saved when a value was pasted/entered into text box.
Sector Edit form: "reset value" button was not shown for light and fade values when selected sectors had different light/fade colors.
Reverted Open Map form changes from previous commit (my assumption that map marker is always empty was not correct...)
Updated documentation.

Snap Map Elements to Grid mode now works much faster and shows a message when completed.
Forced default textures are now only used in drawing modes.
Exception Dialog: long error descriptions were breaking window layout.
Map will no longer be shown in Open Map form if unrelated data is encountered inside of map namespace.

Manual linedef splitting: "Duplicate texture coordinates" and "Reset X coordinate, copy Y coordinate" settings now affect UDMF texture offsets.

"Snap Selected Vertices to Grid" mode: renamed to "Snap Selected Map Elements to Grid". Now it aligns things as well.
Edit forms: some realtime controls were applying relative values incorrectly.

Textures now load up to 2x faster when "mix textures and flats" flag is set in game configuration.
TEXTUREx/TEXTURES: texture will now be created if at least one of it's patches is loaded.
Visual mode: fixed a crash when "Slope floor to here" (9500) or "Slope ceiling to here" (9501) things were not inside sector.
Fixed: flats were not loaded form wads inside Directory and PK3/PK7 resources.
Sector Info Panel, Linedef Info Panel: texture size was shown for unknown textures.

Tag Statistics form: you can now double click on Sectors, Linedefs or Things cell to select them, and right click to open their properties.
Texture size labels were displayed incorrectly in some cases.
Rewritten VerticesMode.DeleteItem() once again...
Vertex Edit form now works in realtime mode.
Vertex Edit form: ceiling and floor vertex offsets can now be cleared.
Added StairSectorBuilder plugin (I suppose some external plugins will stop working in GZDB because I've changed ButtonStep to float in ButtonsNumericTextbox a couple revisions ago...).
Preferences form: action description is now scrollable.
Changed background color of Sector Edit form.
Vertex' ZCeiling and ZFloor properties are now managed internally.

Visual mode, UDMF: added "Scale Texture Up (X)", "Scale Texture Down (X)", "Scale Texture Up (Y)", "Scale Texture Down (Y)" actions. Default keys are Num6, Num4, Num8, Num5.
Visual mode, UDMF: renamed "Rotate Thing Clockwise" and "Rotate Thing Counterclockwise" actions to "Rotate Clockwise" and "Rotate Counterclockwise". These actions can now be used to change rotation of floor/ceiling textures.
Visual mode, UDMF: "Reset Texture Offsets" action now also resets sidedef's scale and floor/ceiling's scale and rotation.
Visual mode, UDMF: control line's OffsetX and OffsetY were not taken into account when calculating texture offsets of 3d floors' sides.
Visual mode, UDMF: fixed a ton of bugs in Auto align functions.
Visual mode, UDMF: when using "Move Texture Left/Right/Up/Down by 1" actions texture offsets were not updated properly when texture's scale was < 1.0.
Visual mode, UDMF: OffsetX and OffsetY were not taken into account in "Fit Texture Width/Height" actions.
Dockers Panel: added Pin/Unpin button, which acts the same as "Preferences -> Interface -> Side panels -> Auto hide" checkbox.
Texture size labels can now be disabled by unchecking "Preferences -> Interface -> Show texture and flat sizes in browsers" checkbox.
Texture size labels now are not shown for unknown textures.
Most of texture size labels had incorrect bg color.
ZDoom_linedefs.cfg: action specials 223 and 224 had incorrect Arg0.

Classic Modes: added 3D floor indication (color can be changed in Preferences -> Appearance -> 3D Floors).
Sector_Set3dFloor action (160): added hi-tag/line ID check.

Classic modes, UDMF: floor/ceiling texture offsets can now be locked in place while sector is dragged.
Fixed another bug in Tools.autoAlignTexturesOnSidesUDMF()
Replaced Math.PI-related equations with stuff from Angle2D class.

Rectangular Selection: removed direction-based additive/subtractive selection. You can now hold Ctrl to enable subtractive selection, hold Ctrl-Shift to intersect with existing selection.
Point Thing at Cursor action: action now works when used from menu, changed default shortcut to Shift-L. You can now hold Ctrl to point Things away from cursor.