Merge branch 'master' into docking

# Conflicts:
#	imgui.cpp
#	imgui.h

docs/CHANGELOG.txt

@@ -110,13 +110,22 @@ Other Changes:
 - InputText: Work-around for buggy standard libraries where isprint('\t') returns true. (#2467, #1336)
 - InputText: Fixed ImGuiInputTextFlags_AllowTabInput leading to two tabs characters being inserted
   if the back-end provided both Key and Character input. (#2467, #1336)
+- Added SetNextItemWidth() helper to avoid using PushItemWidth/PopItemWidth() for single items.
+  Note that SetNextItemWidth() currently only affect the same subset of items as PushItemWidth(),
+  generally referred to as the large framed+labeled items.
+  Because the new SetNextItemWidth() function is explicit
 - GetMouseDragDelta(): also returns the delta on the mouse button released frame. (#2419)
 - GetMouseDragDelta(): verify that mouse positions are valid otherwise returns zero.
 - Inputs: Also add support for horizontal scroll with Shift+Mouse Wheel. (#2424, #1463) [@LucaRood]
 - PlotLines, PlotHistogram: Ignore NaN values when calculating min/max bounds. (#2485)
 - Window: Window close button is horizontally aligned with style.FramePadding.x.
+- Columns: Fixed boundary of clipping being off by 1 pixel within the left column.
+- Combo, Slider, Scrollbar: Improve rendering in situation when there's only a few pixels available (<3 pixels).
+- Misc: Fixed PushItemWidth(-width) (for right-side alignment) laying out certain items (button, listbox, etc.)
+  with negative sizes if the 'width' argument was smaller than the available width at the time of item submission,
 - Misc: Added IM_MALLOC/IM_FREE macros mimicking IM_NEW/IM_DELETE so user doesn't need to revert
   to using the ImGui::MemAlloc()/MemFree() calls directly.
+- Metrics: Added "Show windows rectangles" tool to visualize the different rectangles.
 - Examples: OpenGL: Added a dummy GL call + comments in ImGui_ImplOpenGL3_Init() to detect uninitialized
   GL function loaders early, and help users understand what they are missing. (#2421)
 - Examples: Emscripten: Added Emscripten+SDL+GLES2 example. (#2494, #2492, #2351, #336) [@nicolasnoble]

docs/TODO.txt

@@ -29,13 +29,14 @@ It's mostly a bunch of personal notes, probably incomplete. Feel free to query i
  - window/opt: freeze window flag: if not focused/hovered, return false, render with previous ImDrawList. and/or reduce refresh rate. -> this may require enforcing that it is illegal to submit contents if Begin returns false.
  - window/child: the first draw command of a child window could be moved into the current draw command of the parent window (unless child+tooltip?).
  - window/clipping: some form of clipping when DisplaySize (or corresponding viewport) is zero.
+ - window/tab: add a way to signify that a window or docked window requires attention (e.g. blinking title bar).
  - scrolling: while holding down a scrollbar, try to keep the same contents visible (at least while not moving mouse)
  - scrolling: allow immediately effective change of scroll after Begin() if we haven't appended items yet.
  - scrolling/clipping: separator on the initial position of a window is not visible (cursorpos.y <= clippos.y). (2017-08-20: can't repro)
  - scrolling/style: shadows on scrollable areas to denote that there is more contents
 
  - drawdata: make it easy to clone (or swap?) a ImDrawData so user can easily save that data if they use threaded rendering.
- - drawlist: add calctextsize func to facilitate consistent code from user pov
+ ! drawlist: add calctextsize func to facilitate consistent code from user pov (currently need to use ImGui or ImFont alternatives!)
  - drawlist: end-user probably can't call Clear() directly because we expect a texture to be pushed in the stack.
  - drawlist: maintaining bounding box per command would allow to merge draw command when clipping isn't relied on (typical non-scrolling window or non-overflowing column would merge with previous command).
  - drawlist: primitives/helpers to manipulate vertices post submission, so e.g. a quad/rect can be resized to fit later submitted content, _without_ using the ChannelSplit api
@@ -45,6 +46,7 @@ It's mostly a bunch of personal notes, probably incomplete. Feel free to query i
  - drawlist: rendering: provide a way for imgui to output to a single/global vertex buffer, re-order indices only at the end of the frame (ref: https://gist.github.com/floooh/10388a0afbe08fce9e617d8aefa7d302)
  - drawlist: callback: add an extra void* in ImDrawCallback to allow passing render-local data to the callback (would break API).
  - drawlist: AddRect vs AddLine position confusing (#2441)
+ - drawlist: channel splitter should be external helper and not stored in ImDrawList.
  - drawlist/opt: store rounded corners in texture to use 1 quad per corner (filled and wireframe) to lower the cost of rounding. (#1962)
  - drawlist/opt: AddRect() axis aligned pixel aligned (no-aa) could use 8 triangles instead of 16 and no normal calculation.
  - drawlist/opt: thick AA line could be doable in same number of triangles as 1.0 AA line by storing gradient+full color in atlas.
@@ -372,6 +374,7 @@ It's mostly a bunch of personal notes, probably incomplete. Feel free to query i
  - examples: glfw: could go idle when minimized? if (glfwGetWindowAttrib(window, GLFW_ICONIFIED)) { glfwWaitEvents(); continue; } // issue: DeltaTime will be super high on resume, perhaps provide a way to let impl know (#440)
  - examples: opengl: rename imgui_impl_opengl2 to impl_opengl_legacy and imgui_impl_opengl3 to imgui_impl_opengl? (#1900)
  - examples: opengl: could use a single vertex buffer and glBufferSubData for uploads?
+ - examples: opengl: explicitly disable GL_STENCIL_TEST in bindings.
  - examples: vulkan: viewport: support for synchronized swapping of multiple swap chains.
  - optimization: replace vsnprintf with stb_printf? or enable the defines/infrastructure to allow it (#1038)
  - optimization: add clipping for multi-component widgets (SliderFloatX, ColorEditX, etc.). one problem is that nav branch can't easily clip parent group when there is a move request.