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.

Visual mode: added "Auto-align Textures to Selection (X)", "Auto-align Textures to Selection (Y)" and "Auto-align Textures to Selection (X and Y)" actions.
"Snap Map Elements to Grid" mode now tries to fix invalid geometry after vertex snapping.
Vertices mode: in some cases not all vertices were removed when deleting vertices.
Removed "Load GZDoom light definitions" from preferences. If you want to use GZDoom's GLDEFS definitions, add "lights.pk3" as a resource.
Visual mode: fixed a crash when toggling GZDoom Geometry Effects (Tab)
Fixed sector bounding box calculation error.
Renamed "Edit -> Grid Setup..." to "Edit -> Grid and Backdrop Setup..."
Updated documentation

Error Checking: renamed "Check unclosed sectors" to "Check invalid sectors". Now it also finds sectors with less than 3 sidedefs and sectors, which area is 0.

Changed the way sector bounding box is calculated. This fixes major slowdowns when a sector with invalid geometry (e.g. without triangulation) is highlighted in Classic modes and a crash in Visual mode when such sector is rendered.

Visual mode: fixed a crash when trying to move texture offsets of invisible sidedef.

Sector Info panel: in soma cases texture size was shown for unknown/missing textures.

Sector Edit forms: floor/ceiling textures can be cleared with right-click on texture selectors. 

Renamed "Set current textures" to "Set default textures" (I hope that makes more sense now).
Fixed and updated documentation.

Error Checks mode: connected lines with decimal positions were reported as overlapping in some cases.

Fixed "Snap Map Element to Grid" documentation.

"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.

Replaced editor sprite for "Teleport (Z Height and Gravity)" and "Teleport (Z Height)" things with internal one, because old sprite was Doom-specific and was not shown properly in other game configurations.

Classic modes: 3D floor indicators can be disabled in preferences (Preferences -> Appearance -> Mark 3D floors in classic modes).
Updated documentation.

Visual mode: fixed a crash when trying to load non existing sprite, defined in configuration or via "//@sprite" parameter in DECORATE.
MissingThing icon is now used when the editor is unable to load thing sprite.
An error is added to error logger when the editor is unable to load thing sprite.

Fixed a crash when executing "Toggle Geometry Effects" (Tab).

Increased maximum zoom level in Classic modes to 3000%.
Added "1 mp" option in grid size menu.
Added "400%" option in zoom menu.
Renamed "Toggle GZDoom rendering effects" action to "Toggle Geometry Effects".
Sync camera position: Visual Camera height is now changed only if camera is above or below current sector.
Classic modes: view was not redrawn after "Test map from current position" action.
"Test map from current position" action: incorrect player start was used when a map had several Player 1 Start things.

Some cosmetic changes in Linedef Edit form.
Link, Unlink and Reset icons can now be properly seen on dark backgrounds.

Tag and script number/name drop downs in Edit forms are now resized to match the width of the longest entry. 
Jitter mode: view was not updated when "Relative" option was toggled.

Some cosmetic changes in uifields management.

Color picked plugin: plugin used incorrect default "lightcolor" value after r1758.

UDMF fields, handled by UI, had broken field types after r1758.
Removed some redundant type casts.

UDMF: added "gravity" thing property to UI.
MAPINFO parser: removed unneeded error notification. 

Made map detection logic a bit more strict. If BEHAVIOUR lump is present, a map can no longer be detected as a map in Doom map format.

"Look Through Selection" action: InterpolationPoint can be handled the same way as SecurityCamera or AimingCamera.

Visual mode: added "Look Through Selection" action (default key is "Y"). This action places visual camera at the same position as selected/highlighted thing and rotates it to match thing's angle. Special handling is available if targeted thing is AimingCamera, MovingCamera or SecurityCamera.
Script editor: pressing "F1" now opens keyword help instead of program manual.
Linedef edit form, Thing edit form: rewritten script support logic. It should now work in the same manner as the rest of controls.
Thing info panel: thing arguments now have proper labels.
Edit forms, UDMF: fields, which are handled by UI, are no longer shown in "Custom" tab.
Visual mode: fixed a crash when loading a model on a video card without Shader model 2.0 support.
Fixed incorrect argument number and changed most of labels in "Cameras and interpolation" section of zdoom_things.cfg.