Issue numbers (#) refer to github issues listed at https://github.com/ocornut/imgui/issues/XXXX
The list below consist mostly of ideas noted down before they are requested/discussed by users (at which point they usually exist on the github issue tracker).
It's mostly a bunch of personal notes, probably incomplete. Feel free to query if you have any questions.
- window: calling SetNextWindowSize() every frame with <= 0 doesn't do anything, may be useful to allow (particularly when used for a single axis). (#690)
- window: add a way for very transient windows (non-saved, temporary overlay over hundreds of objects) to "clean" up from the global window list. perhaps a lightweight explicit cleanup pass.
- window: using SetWindowPos() inside Begin() and moving the window with the mouse reacts a very ugly glitch. We should just defer the SetWindowPos() call.
- 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.
- 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
- drawlist: would be good to be able to deep copy of ImDrawData (we have a deep copy of ImDrawList now).
- 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)
- main: find a way to preserve relative orders of multiple reappearing windows (so an app toggling between "modes" e.g. fullscreen vs all tools) won't lose relative ordering.
- main: IsItemHovered() make it more consistent for various type of widgets, widgets with multiple components, etc. also effectively IsHovered() region sometimes differs from hot region, e.g tree nodes
- main: IsItemHovered() info stored in a stack? so that 'if TreeNode() { Text; TreePop; } if IsHovered' return the hover state of the TreeNode?
- widgets: a way to represent "mixed" values, so e.g. all values replaced with **, including check-boxes, colors, etc. with support for multi-components widgets (e.g. SliderFloat3, make only "Y" mixed)
- input text: add discard flag (e.g. ImGuiInputTextFlags_DiscardActiveBuffer) or make it easier to clear active focus for text replacement during edition (#725)
- input text: display bug when clicking a drag/slider after an input text in a different window has all-selected text (order dependent). actually a very old bug but no one appears to have noticed it.
- input text multi-line: don't directly call AddText() which does an unnecessary vertex reserve for character count prior to clipping. and/or more line-based clipping to AddText(). and/or reorganize TextUnformatted/RenderText for more efficiency for large text (e.g TextUnformatted could clip and log separately, etc).
- input text multi-line: line numbers? status bar? (follow up on #200)
- input text multi-line: behave better when user changes input buffer while editing is active (even though it is illegal behavior). namely, the change of buffer can create a scrollbar glitch (#725)
- input text multi-line: better horizontal scrolling support (#383, #1224)
- layout: helper or a way to express ImGui::SameLine(ImGui::GetCursorStartPos().x + ImGui::CalcItemWidth() + ImGui::GetStyle().ItemInnerSpacing.x); in a simpler manner.
- layout: generalization of the above: a concept equivalent to word processor ruler tab stop ~ mini columns (position in X, no clipping implied) (vaguely relate to #267, #395, also what is used internally for menu items)
- plot: add a helper e.g. Plot(char* label, float value, float time_span=2.0f) that stores values and Plot them for you - probably another function name. and/or automatically allow to plot ANY displayed value (more reliance on stable ID)
- dock: B~ rework code to be able to lazily create tab bar instance in a single place. The _Unsorted tab flag could be replacing a trailing-counter in DockNode?
- dock: B~ fully track windows/settings reference in dock nodes. perhaps find a representation that allows facilitate use of dock builder functions.
- dock: B~ Unreal style document system (requires low-level controls of dockspace serialization fork/copy/delete). this is mostly working but the DockBuilderXXX api are not exposed/finished.
- dock: B- dock node inside its own viewports creates 1 temporary viewport per window on startup before ditching them (doesn't affect the user nor request platform windows to be created, but unnecessary)
- dock: B~ SetNextWindowDock() calls (with conditional) -> defer everything to DockContextUpdate (repro: Documents->[X]Windows->Dock 1 elsewhere->Click Redock All
- dock: B~ tidy up tab list popup buttons features (available with manual tab-bar, see ImGuiTabBarFlags_NoTabListPopupButton code, not used by docking nodes)
- dock: B- SetNextWindowFocus() doesn't seem to apply if the window is hidden this frame, need repro (#4)
- dock: B- resizing a dock tree small currently has glitches (overlapping collapse and close button, etc.)
- dock: B- dpi: look at interaction with the hi-dpi and multi-dpi stuff.
- dock: B- tab bar: appearing on first frame with a dumb layout would do less harm that not appearing? (when behind dynamic branch) or store titles + render in EndTabBar()
- dock: B- tab bar: make selected tab always shows its full title?
- dock: B- nav: design interactions so nav controls can dock/undock
- dock: C- nav: CTRL+TAB highlighting tabs shows the mismatch between focus-stack and tab-order (not visible in VS because it doesn't highlight the tabs)
- dock: C- after a dock/undock, the Scrollbar Status update in Begin() should use an updated e.g. size_y_for_scrollbars to avoid a 1 frame scrollbar flicker.
- image/image button: misalignment on padded/bordered button?
- image/image button: parameters are confusing, image() has tint_col,border_col whereas imagebutton() has bg_col/tint_col. Even thou they are different parameters ordering could be more consistent. can we fix that?
- slider/drag: ctrl+click when format doesn't include a % character.. disable? display underlying value in default format? (see InputScalarAsWidgetReplacement)
- listbox: make it easier/more natural to implement range-select (need some sort of info/ref about the last clicked/focused item that user can translate to an index?) (wip stash)
!- popups/menus: clarify usage of popups id, how MenuItem/Selectable closing parent popups affects the ID, etc. this is quite fishy needs improvement! (#331, #402)
- popups: reopening context menu at new position should be the behavior by default? (equivalent to internal OpenPopupEx() with reopen_existing=true) (~#1497)
- tooltip: drag and drop with tooltip near monitor edges lose/changes its last direction instead of locking one. The drag and drop tooltip should always follow without changing direction.
- tooltip: tooltips with delay timers? or general timer policy? (instantaneous vs timed): IsItemHovered() with timer + implicit aabb-id for items with no ID. (#1485)
- text: it's currently impossible to have a window title with "##". perhaps an official workaround would be nice. \ style inhibitor? non-visible ascii code to insert between #?
- style: a concept of "compact style" that the end-user can easily rely on (e.g. PushStyleCompact()?) that maps to other settings? avoid implementing duplicate helpers such as SmallCheckbox(), etc.
- style: try to make PushStyleVar() more robust to incorrect parameters (to be more friendly to edit & continues situation).
- style: global scale setting.
- style: WindowPadding needs to be EVEN as the 0.5 multiplier used on this value probably have a subtle effect on clip rectangle
- log: have more control over the log scope (e.g. stop logging when leaving current tree node scope)
- log: be able to log anything (e.g. right-click on a window/tree-node, shows context menu? log into tty/file/clipboard)
- log: let user copy any window content to clipboard easily (CTRL+C on windows? while moving it? context menu?). code is commented because it fails with multiple Begin/End pairs.
- drag and drop: make it easier and provide a demo to have tooltip both are source and target site, with a more detailed one on target site (tooltip ordering problem)
- font: enforce monospace through ImFontConfig (for icons?) + create dual ImFont output from same input, reusing rasterized data but with different glyphs/AdvanceX
- font: storing MinAdvanceX per font would allow us to skip calculating line width (under a threshold of character count) in loops looking for block width
- font: optimization: for monospace font (like the default one) we can trim IndexXAdvance as long as trailing value is == FallbackXAdvance (need to make sure TAB is still correct), would save on cache line.
- font: add support for kerning, probably optional. A) perhaps default to (32..128)^2 matrix ~ 9K entries = 36KB, then hash for non-ascii?. B) or sparse lookup into per-char list?
- font: add a simpler CalcTextSizeA() api? current one ok but not welcome if user needs to call it directly (without going through ImGui::CalcTextSize)
- font: fix AddRemapChar() to work before font has been built.
- font: (api breaking) remove "TTF" from symbol names. also because it now supports OTF.
- font/opt: Considering storing standalone AdvanceX table as 16-bit fixed point integer?
- font/opt: Glyph currently 40 bytes (2+9*4). Consider storing UV as 16 bits integer? (->32 bytes). X0/Y0/X1/Y1 as 16 fixed-point integers? Or X0/Y0 as float and X1/Y1 as fixed8_8?
- nav: wrap around logic to allow e.g. grid based layout (pressing NavRight on the right-most element would go to the next row, etc.). see internal's NavMoveRequestTryWrapping().
- nav: restore/find nearest navid when current one disappear (e.g. pressed a button that disappear, or perhaps auto restoring when current button change name)
- nav: SetItemDefaultFocus() level of priority, so widget like Selectable when inside a popup could claim a low-priority default focus on the first selected iem
- nav: NavFlattened: broken: in typical usage scenario, the items of a fully clipped child are currently not considered to enter into a NavFlattened child.
- nav/menus: pressing left-right on a vertically clipped menu bar tends to jump to the collapse/close buttons.
- nav/menus: allow pressing Menu to leave a sub-menu.
- nav/menus: a way to access the main menu bar with Alt? (currently needs CTRL+TAB)
- nav/menus: when using the main menu bar, even though we restore focus after, the underlying window loses its title bar highlight during menu manipulation. could we prevent it?
- nav: when activating a button that changes label (without a static ID) or disappear, can we somehow automatically recover into a nearest highlight item?
- nav: there's currently no way to completely clear focus with the keyboard. depending on patterns used by the application to dispatch inputs, it may be desirable.
- nav: configuration flag to disable global shortcuts (currently only CTRL-tab) ?
- viewport: use getfocus/setfocus api to synchronize imgui<>platform focus better (e.g imgui-side ctrl-tab can focus os window, OS initial setup and alt-tab can focus imgui window etc.)
- viewport: implicit/fallback Debug window can hog a zombie viewport (harmless, noisy?) > could at least clear out the reference on a per session basis?
- platform: sdl: no support for ImGuiBackendFlags_HasMouseHoveredViewport. maybe we could use SDL_GetMouseFocus() / SDL_WINDOW_MOUSE_FOCUS if imgui could fallback on its heuristic when NoInputs is set
- platform: sdl: no refresh of monitor/display (SDL doesn't seem to have an event for it).
- inputs: we need an explicit flag about whether the imgui window is focused, to be able to distinguish focused key releases vs alt-tabbing all release behaviors.
- misc: idle: if cursor blink if the _only_ visible animation, could even expose a dirty rectangle that optionally can be leverage by some app to render in a smaller viewport, getting rid of much pixel shading cost.
- emscriptem: with refactored examples, we could provide a direct imgui_impl_emscripten platform layer (see eg. https://github.com/floooh/sokol-samples/blob/master/html5/imgui-emsc.cc#L42)
- 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)
- 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.
- optimization: add a flag to disable most of rendering, for the case where the user expect to skip it (#335)
- optimization: use another hash function than crc32, e.g. FNV1a
- optimization/render: merge command-lists with same clip-rect into one even if they aren't sequential? (as long as in-between clip rectangle don't overlap)?
- optimization: turn some the various stack vectors into statically-sized arrays
