Added, Draw Grid mode: "Lock slices to grid" now operates in 4 modes: "None", "Horizontal", "Vertical" and "Both". Can be helpful when drawing ladders and such.
Changed, all drawing modes: changeable drawing mode settings are now persistent.
Changed: "Dynamic grid size" mode is now disabled when changing grid size manually.
Documentation: "Command Line Parameters" topic contained a lot of incorrect information...
Updated ZDoom_DECORATE.cfg.

+A couple of cosmetic tweaks and fixes.
Updated ZDoom_DECORATE.cfg.

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.

Added "Fixed Things Scale" setting (available in the View menu, as a button on the View toolbar and as the "Toggle Fixed Things Scale" action). When enabled, Things will no longer be scaled based on current zoom level in Classic modes, instead, thing bounding box will be drawn when appropriate (this option mimics DB1 things rendering style).
Internal: removed some remnants of fixed rendering pipeline from Renderer2D and Renderer3D.

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

Added, "Find Thing Action and Arguments" search mode: "Any action" (-1) can now be used as a search input.
Fixed, "Find Linedef Action and Arguments" and "Find Sector Effect" search modes: in some cases action/effect was checked incorrectly when performing a search. 

Added, "Find Linedef Action and Arguments" search mode: "Any action" (-1) can now be used as a search input.
Added, "Find Sector Effect" search mode: "Any effect" (-1) can now be used as a search input.
Fixed, "Find Linedef Action and Arguments" search mode: generalized actions search was broken.
Fixed, General interface: in some cases the placeholder test engine was displayed in the "Test Map" drop-down.

Added, all drawing modes: added "Continuous drawing" option (available in the top mode menu / Draw Grid panel for the Draw Grid mode). When enabled, drawing mode will not be switched to previously active mode after finishing drawing a shape.
Fixed, general interlace: in some cases "Show Editable Vertices in Visual Mode" top toolbar button showed up when using Doom/Hexen map formats.
Fixed(?), Classic modes: probably fixed an rare issue when map element dragging was not starting when supposed to.

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.

Fixed, Things mode: Undo for things cloning by Shift-dragging them was created incorrectly (cloned things were moved to their initial position, but not removed).
Fixed, Visual mode: fixed Classic sky texture generation artifact when Bilinear filtering was enabled in Visual mode.
Fixed, Visual mode: fixed Classic sky texture generation artifact when non-power-of-2 Sky textures were used.
Fixed, Visual mode: dynamic lights flickering on surfaces nearly-perpendicular to lights centers should be much harder to trigger now.

Fixed, Visual mode: some video memory was not released after closing a map if the Visual mode was enabled at least once during the editing session, eventually resulting in E_OUTOFMEMORY crash.
Fixed, General interface, cosmetic: in some cases the warnings label was disabled in a flashing state (e.g. with red background).
Internal: moved some older GZDB actions form GZGeneral to MapManager. They can no longer be toggled when no map is loaded (which is probably for the best).
Updated ZDoom_ACS.cfg.
Updated ZDoom_DECORATE.cfg.

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 a crash when trying to parse an empty TEXTURES lump (probably covers some other empty text lumps as well).
Added strict revision checking to BuilderModes.dll (this plugin must always stay in sync with the core).

Fixed, Map conversion: game mode flags were ignored when converting from Doom map format to UDMF.
Fixed, Edit Selection mode: when "Drag selection automatically on paste" setting was enabled, it was possible to start rotating/scaling map elements instead of dragging them after pasting.

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.

Fixed, Visual mode: fixed D3DERR_INVALIDCALL error caused by a bug in classic skybox texture creation.
Fixed, Visual mode: aspect ratio was not updated when render area was resized.
Fixed, Visual mode: vertex handles were disappearing after using Reload Resources (F8) action.
Changed, internal: removed most of the fixed pipeline rendering code. The editor can no longer be used on a video card without Shader Model 2.0 support. 

Fixed, Visual mode: "Select with the same texture" action should not select invisible geometry (like sidedef parts hidden by slopes).
Changed, Sector drawing: default sector height is now used when the nearest sector's height is <= 0.

Fixed, Visual mode: "render as sky" flag was not updated for upper wall geometry when pasting textures (and in some other cases).

Added "Toggle sky rendering" action and toolbar button.
Added, MAPINFO parser: the editor now recognizes map number from classic map definition format. Hexen MAPINFO is now properly parsed.
Added, MAPINFO support: if current map definition contains map name as a text string, it will be shown in the editor's header.
Changed: "Toggle dynamic lights rendering" now toggles between "Don't show dynamic lights" and "Show dynamic lights" when used in Classic modes. 
Changed, Things mode: lowered the opacity of dynamic light radii.
Changed, (G)ZDoom text parsers: empty include files now trigger a warning instead of an error and no longer abort parsing.
Fixed, Game configurations: moved Stalagmite:5050 thing to Doom block (so the editor no longer tries to load it for non-Doom game configurations).
Fixed(?), Visual mode: probably fixed a hard-to-trigger exception when sorting translucent geometry.
Fixed, Visual mode: floor glow effect was incorrectly applied to walls (was broken in R2452).
Internal: restructured most of MAPINFO and GLDEFS parsers. Should be more maintainable now.  
Updated ZDoom ACC.
Updated zdbsp to 1.19.
Updated documentation.

Fixed a crash after pressing "Edit Selection" button in the Find and Replace window when several instances of the same map element were selected.
Redesigned the Test Map button's drop-down: test engines are now shown and behave the same way as skills and also have appropriate icons. 

Fixed, Map Analysis mode, "Check stuck things" check: rewritten parts of the flags checking logic to allow more accurate flag checks.
Fixed, Map Analysis mode: fixed a crash when trying to dissolve an invalid sector when one of it's linedefs referenced it on the both sides.
Fixed, Sectors mode: fixed incorrect undo description when deleting sectors.
Internal: joined declaration and assignment of some more variables.

Internal: joined declaration and assignment of some variables.

Updated ZDoom ACC and ZDoom_ACS.cfg (added GetInventoryMax()).

Added, Things mode: dynamic light things light radii are now rendered (can be disabled by setting "Dynamic light mode" to "Don't show dynamic lights" on the top toolbar).
Internal, Renderer2D.RenderArrows(): only visible lines are now rendered.
Internal, API: renamed public Line3D properties: v1 to Start, v2 to End, color to Color, renderarrowhead to RenderArrowhead.

Changed, "Select Similar", "Paste Properties Special" actions properties windows, Linedefs: removed "Sidedef Properties" from Linedef flags tab.
Fixed several issues with "Synchronized Things Selection" setting:
- Things were not deselected after dragging a single sector.
- Things were not deselected after editing properties of a single sector.
- Things sector references were not updated after using "Join Sectors" and "Merge Sectors" actions.
- Things (de)selection is now applied to all things, instead of only the ones visible using current Things Filter.

Cosmetic, actions: renamed "Lower Floor/Ceiling by 8 mp" to "Lower Floor/Ceiling/Thing by 8 mp", "Raise Floor/Ceiling by 8 mp" to "Raise Floor/Ceiling/Thing by 8 mp", "Lower Floor/Ceiling by 1 mp" to "Lower Floor/Ceiling/Thing by 1 mp", "Raise Floor/Ceiling by 1 mp" to "Raise Floor/Ceiling/Thing by 1 mp", "Lower Floor/Ceiling to adjacent sector" to "Lower Floor/Ceiling/Thing to adjacent Sector/Thing", "Raise Floor/Ceiling to adjacent sector" to "Raise Floor/Ceiling/Thing to adjacent Sector/Thing".
Updated, Visual mode, "Raise Floor/Ceiling/Thing to adjacent Sector/Thing" / "Lower Floor/Ceiling/Thing to adjacent Sector/Thing" actions: sectors across targeted sectors are now taken into account when determining target height.
Updated, Visual mode, "Raise Floor/Ceiling/Thing to adjacent Sector/Thing" / "Lower Floor/Ceiling/Thing to adjacent Sector/Thing" actions: the actions can now stack things on top of other things when their bounding boxes intersect. 
Internal: cosmetic changes to shader update logic.
Internal: thing bounding box is now used when adding a thing to VisualBlockMap.

Fixed, Visual mode: fixed a crash when showing Edit Vertex window when several selected vertices belonged to the same sector.

Fixed, Visual mode: in some cases fog density of 3d floor floors/ceilings was calculated incorrectly. 

Fixed, Visual mode, "Auto-align textures" actions, UDMF: vertical offsets of non-wrapped middle textures should not be clamped.
Fixed, Visual mode: brightness of 3d floors with "disable lighting" flag was calculated incorrectly.
Fixed, Sectors mode: 3d floor linedef indicators were not updated after using "Join Sectors" and "Merge Sectors" actions.

Fixed, Visual mode, fog rendering: things with Bright setting should still be affected by custom fade.
Updated ZDoom_DECORATE.cfg.

Fixed, Visual mode: fixed incorrect GLDEFS glow brightness calculation for Things.
Updated ZDoom_DECORATE.cfg.