Minor comments, tweaks

Merge branch 'master' into drag_and_drop

Drag and Drop: Added payload->IsPreview() to user can render their custom preview while handling overlapping drop targets. (#143)

io.OptNoCursorBlink -> io.OptCursorBlink (#1427)

Added io.OptNoCursorBlink option to disable cursor blinking. (#1427). Renamed io.OSXBehaviors to io.OptMacOSXBehaviors. Should affect users as the compile-time default is usually enough. (#473, #650)

Drag and Drop: Moved internal fields out of public sight. (#143)

Drag and Drop: Rework internal to allow overlapping targets (#143)

Merge branch 'master' into drag_and_drop

IsWindowHovered(): Added ImGuiHoveredFlags_FlattenChilds flag. Made IsRootWindowOrAnyChildHovered() obsolete in favor of IsWindowHovered( ImGuiHoveredFlags_FlattenChilds) (#1382, #1404)

Update imgui.h

Drag and Drop: Added ImGuiDragDropFlags_SourceNoHoldToOpenOthers flag.

Examples: Added a bunch of comments/referencs related to io.WantCaptureMouse, io.WantCaptureKeyboard (#1262, #1237, #1219, #635, #1058, #1051, #912, #533, #703, #446, #459, #364, #213, #52, and more)

Demo: Comments (#1408)

Added assertions and comments for incorrect use/understanding of IsWindowFocused() etc. functions

Drag and Drop: Added a mechanism to allow widgets with no identifiers (such as Text/Image) to be used with BeginDragDropSource() given the explicit ImGuiDragDropFlags_SourceAllowNullID flag.

Drag and drop: moved to imgui.h

Examples: Added more comments near the fonts loading section, to catch common questions and errors (e.g. #1397, #1366, #1341, #1222, #1193, #1115, #951, etc.)

Styles: Moved Classic colors code to imgui_draw.cpp. Sneakily added a StyleColorsDark() function.

Version 1.53 WIP

IO: Tracking extra mouse dragging data which is convenient for implementating various manual drag and drop patterns.

Version 1.52

Comments

NewFrame: Allow MovedWindow setting the ImGuiWindowFlags_NoInputs after moving has started in order to be able to detect windows below it, which is useful for e.g. docking mechanisms.

Exposed IM_ARRAYSIZE() in imgui.h

Font: Renamed ImFont::Clear() to ImFont::ClearOutputData() for consistency with what ImFontAtlas does. DisplayOffset is set by constructor but not reset by ClearOutputData. (#1349)

Added OpenPopupOnItemClick(); helper which mimic BeginPopupContextItem() but doesn't do the open. ...

Made the color popups uses this standard function so they handle reopening a context menu.

IsItemHovered(), IsWindowHovered(): added flags to enable various and more specific behavior. Will enable improvements for popups/context menus and drag'n drop. (relate ~#439, #1013, #143, #925) ...

The legacy confusing IsItemRectHovered(), IsWindowRectHovered() can be completely removed now.
Changed IsWindowHovered() behavior with default parameter: it now return false is the window is blocked by a popup.
Demo: Added tests for those two functions.

Moved IMGUI_DISABLE_OBSOLETE_FUNCTIONS block lower in the imgui.h file so obsolete functions can use flags. Also sane to quarantine them outside of the respectable area.

IO: reordering some supposedly private fields.

Begin: Marked 5 parameters version of Begin() as obsolete. Now waiting for a riot to happen!