Help users if they are reusing the same ID (Fix #7669) #7961
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(fix for ocornut#7669) There is a common user issue which is that developers may reuse the same ID, and will not understand why their widget is not responsive. This PR will: * detect when the same ID is used on different widgets (only if the widget is hovered, to avoid a O(n^2) search at each frame) * display a warning tooltip to the user, with hints on how to fix the issue (e.g. use PushID, or add a ## to the label) * allow the user to break in the debugger on any of the widgets that use the same ID * enable to disable the warning when needed (e.g. when reusing the ID is intentional, via PushAllowDuplicateID / PopAllowDuplicateID) * enable to debug all duplicates at once (by defining IMGUI_DEBUG_PARANOID) **View from 10,000 feet** 1. This PR adds a distinction between ```cpp // Same as before ImGuiID GetID(const char* str, const char* str_end = NULL); ``` and ```cpp // returns GetID(), but may display a warning tooltip if the ID is not unique. Should be called only once per frame with a given ID stack. ImGuiID ReserveUniqueID(const char* str_id); ``` This distinction was applied to several widgets inside imgui_widgets.cpp which now call ReserveUniqueID instead of GetID, when their intention is to reserve a unique ID for the widget. 2. For grepability, most of the changes are highlighted with a comment `// TRKID`. The only changes which are not marked with this are where GetID() was simply replace by ReserveUniqueID() inside imgui_widgets.cpp These `// TRKID` comments should be removed before merging, and they are only here to help reviewing the changes. 3. The full `ImGui::ShowDemoWindow()` was reviewed to make sure that no duplicated ID was used. Very few changes were required, and they are detailed in the PR. 4.See this video for a quick overview of the feature and how it is implemented: https://traineq.org/ImGui/ImGui_PR_Warn_reuse_ID_Explanation.mp4 ---- > _Note: if desired, a compile flag (e.g. IMGUI_NO_WARN_DUPLICATE_ID or its inverse) could be added to disable the warning and make ReserveUniqueID behave like GetID()_ Summary of changes ================== struct ImGuiContext: added fields UidIXXX (UidsThisFrame & co) -------------------------------------------------------------- Inside imgui_internal.h / struct ImGuiContext ```cpp struct ImGuiContext { ... // Declaration ImVector<ImGuiID> UidsThisFrame; // A list of item IDs submitted this frame (used to detect and warn about duplicate ID usage). int UidAllowDuplicatesStack; // Stack depth for allowing duplicate IDs (if > 0, duplicate IDs are allowed). See PushAllowDuplicateID / PopAllowDuplicateID ImGuiID UidHighlightedDuplicate; // Will be set if a duplicated item is hovered (all duplicated items will appear with a red dot in the top left corner on the next frame) int UidHighlightedTimestamp; // Timestamp (FrameCount) of the highlight (which will be shown on the next frame) bool UidWasTipDisplayed; // Will be set to true to avoid displaying multiple times the same tooltip ... // Constructor ImGuiContext(ImFontAtlas* shared_font_atlas) { ... UidsThisFrame.clear(); UidAllowDuplicatesStack = 0; UidHighlightedDuplicate = 0; UidHighlightedTimestamp = 0; UidWasTipDisplayed = false; ... } }; ``` struct ImGuiWindow: added ReserveUniqueID(), beside GetID() ----------------------------------------------------------- imgui_internal.h / near GetID() existing methods ```cpp struct ImGuiWindow { ... // ReserveUniqueID: returns GetID(), but may display a warning. Should be called only once per frame with a given ID ImGuiID ReserveUniqueID(const char* str_id); ... }; ``` Added PushAllowDuplicateID / PopAllowDuplicateID ------------------------------------------------ imgui_internal.h / near related ID functions (SetActiveID, GetIDWithSeed, ...) ```cpp ... IMGUI_API void PushAllowDuplicateID(); // Disables the tooltip warning when duplicate IDs are detected. IMGUI_API void PopAllowDuplicateID(); // Re-enables the tooltip warning when duplicate IDs are detected. ... ``` imgui.cpp:3873 / near ReserveUniqueID() implementation ```cpp IMGUI_API void ImGui::PushAllowDuplicateID() { ImGuiContext& g = *GImGui; g.UidAllowDuplicatesStack++; } IMGUI_API void ImGui::PopAllowDuplicateID() { ImGuiContext& g = *GImGui; IM_ASSERT(g.UidAllowDuplicatesStack > 0 && "Mismatched PopAllowDuplicateID()"); g.UidAllowDuplicatesStack--; } ``` > _Note: doing this via ItemFlags was not feasible as many items (e.g. Button, Checkbox) do not expose flags_ Main logic: ImGui::EndFrame(), NewFrame() and ImGuiWindow::ReserveUniqueID() ---------------------------------------------------------------------------- ### ImGui::NewFrame(): ```cpp ... g.UidsThisFrame.resize(0); // Empty the list of items, but keep its allocated data g.UidWasTipDisplayed = false; ``` ### ImGui::EndFrame(): ```cpp IM_ASSERT(g.UidAllowDuplicatesStack == 0 && "Mismatched Push/PopAllowDuplicateID"); if (g.UidHighlightedTimestamp != ImGui::GetFrameCount()) { g.UidHighlightedTimestamp = 0; g.UidHighlightedDuplicate = 0; } ``` ### ImGuiWindow::ReserveUniqueID() in imgui.cpp, at the end of "[SECTION] ID STACK". The pseudocode below summarizes its behavior: ```cpp IMGUI_API ImGuiID ImGuiWindow::ReserveUniqueID(const char* str_id) { ImGuiContext& g = *GImGui; ImGuiID id = GetID(str_id); // If PushAllowDuplicateID was called, do not check for uniqueness if (g.UidAllowDuplicatesStack != 0) return id; // Visual aid: a red circle in the top-left corner of all widgets that use a duplicate of the id if (id == g.UidHighlightedDuplicate) Draw Red dot on top left corner // Only check for uniqueness if hovered (this avoid a O(n^2) search at each frame) if (id == ImGui::GetHoveredID()) { if (g.UidsThisFrame.contains(id) && !g.UidWasTipDisplayed) { // Prepare highlight on the next frame for widgets that use this ID g.UidHighlightedDuplicate = id; g.UidHighlightedTimestamp = ImGui::GetFrameCount(); if (ImGui::BeginTooltip()) { if (! g.DebugItemPickerActive) { // Display tooltip showing the duplicate Id as a string ... // Show hints for correction (PushID, ##) ... ImGui::Text(" Press Ctrl-P to break in any of those items "); if Ctrl-P g.DebugItemPickerActive = true; } else { // Add additional info at the bottom of the ItemPicker tooltip ImGui::Text("Click on one of the widgets which uses a duplicated item"); } ImGui::EndTooltip(); } g.UidWasTipDisplayed = true; } } g.UidsThisFrame.push_back(id); return id; } ``` imgui_widgets.cpp ----------------- **Use ReserveUniqueID, allow duplicates when needed (TempInputText, BeginMenuEx)** I went through all the usages of window->GetID() and changed them to ReserveUniqueID when it was possible / desirable. ### Places with one-line changes In all the places below, the change was extremely simple: I simply replaced `window->GetID` by `window->ReserveUniqueID`. For example, in ImGui::ButtonEx ```cpp bool ImGui::ButtonEx(const char* label, const ImVec2& size_arg, ImGuiButtonFlags flags) ... const ImGuiID id = window->ReserveUniqueID(label); // Instead of window->GetID ``` Below is the list of all function where this simple change was applied: ```cpp InvisibleButton ArrowButtonEx GetWindowScrollbarID ImageButton (both versions) Checkbox RadioButton BeginCombo DragScalar SliderScalar VSliderScalar InputTextEx ColorButton CollapsingHeader Selectable PlotEx BeginTabBar TextLink TreeNode(const char *) TreeNodeEx(const char *) TreeNodeExV(const char *) ``` ### Places where duplicates are needed #### TempInputText TempInputText create text input in place of another active widget (e.g. used when doing a CTRL+Click on drag/slider widgets). It reuses the widget ID, so we allow it temporarily via PushAllowDuplicateID / PopAllowDuplicateID ```cpp bool ImGui::TempInputText(const ImRect& bb, ImGuiID id, const char* label, char* buf, int buf_size, ImGuiInputTextFlags flags) { ImGui::PushAllowDuplicateID(); ... ImGui::PopAllowDuplicateID(); } ``` #### GetWindowScrollbarID GetWindowScrollbarID had to be split in two: ReserveWindowScrollbarID will perform the ID reservation, while GetWindowScrollbarID is only a query. Luckily, this is the only instance where this was required. #### BeginMenuEx In BeginMenuEx, we initially call GetID() instead of ReserveUniqueID() because were are not "consuming" this ID: instead, we are only querying IsPopupOpen(). The ID will be consumed later by calling ImGui::PushID(label) + Selectable("") (which will lead to the same ID) ```cpp bool ImGui::BeginMenuEx(const char* label, const char* icon, bool enabled) { const ImGuiID id = window->GetID(label); bool menu_is_open = IsPopupOpen(id, ImGuiPopupFlags_None); ... PushID(label); pressed = Selectable("", menu_is_open, selectable_flags, ImVec2(w, label_size.y)); ... } ``` ### Places with no changes, but worth mentioning * TreeNode(const void *): unchanged `TreeNode(const void* ptr_id)` and `TreeNodeExV(const void *)` are the only instances which call `window->GetID(const void *)`. As a consequence, they cannot use the unique id mechanism, but I think their usage is rare enough that is not a big concern. * ImGui::TabBarCalcTabID: unchanged It still uses window->GetID, to avoid issues when merging with the docking branch. * BeginChild, BeginPopup and co are unchanged: since they use ImGui::Begin()/End() internally), I suspect they might be called multiple times with the same string, since it is allowed with ImGui::Begin/End. imgui_demo.cpp: some minor changes ---------------------------------- I went through the full demo Window to look for instances where a duplicate ID might be used, and corrected them. Very few changes were required: * **"Layout/Text Baseline Alignment"**: simple ID fix (Added ##) * **"Widgets/Plotting"**: simple id fix (Added ##) * **"Columns (legacy API)/Borders"**: added ImGui::PushID for each cell * **"Widgets/Drag and Drop/Drag to reorder items (simple)"**: no change, but a transient duplicate ID may appear during reordering (for *one* frame only: see comments in the code) Demo code in order to test this PR ================================== Add and call this function in any imgui example. This code will trigger the warnings for duplicated IDs, and will also enable to make sure that the fixes that had to be done are OK. ```cpp char text1[500] = "Hello,"; char text2[500] = "world!"; char text3[500] = "Hello,"; char text4[500] = "world!"; int value = 0; bool flag1 = false, flag2 = false; float f1 = 0.f, f2 = 0.f, f3 = 0.f, f4 = 0.f; void Gui() { // Some widgets to show the duplicated ID warnings ImGui::SetNextWindowSize(ImVec2(400, 500)); if (ImGui::Begin("Duplicated ID examples", nullptr, ImGuiWindowFlags_MenuBar)) { ImGui::TextWrapped("Example of widgets using duplicated IDs"); ImGui::Separator(); ImGui::TextWrapped("Only the first button is clickable (same ID)"); if (ImGui::Button("button")) printf("Button1 pressed\n"); if (ImGui::Button("button")) printf("Button2 pressed\n"); ImGui::Separator(); ImGui::TextWrapped("Those text inputs will share the same value (editing one will overwrite the other)"); ImGui::InputText("text", text1, IM_ARRAYSIZE(text1)); ImGui::InputText("text", text2, IM_ARRAYSIZE(text2)); ImGui::Separator(); ImGui::TextWrapped("Those radio buttons will share the same value (selecting one will overwrite the other)"); ImGui::RadioButton("radio", &value, 0); ImGui::RadioButton("radio", &value, 1); ImGui::Separator(); ImGui::TextWrapped("The second checkbox cannot be toggled"); ImGui::Checkbox("checkbox", &flag1); ImGui::Checkbox("checkbox", &flag2); ImGui::Separator(); ImGui::TextWrapped("Those two sliders will share the same value (editing one will overwrite the other"); ImGui::SliderFloat("slider", &f1, 0.f, 1.f); ImGui::SliderFloat("slider", &f2, 0.f, 1.f); ImGui::Separator(); } ImGui::End(); // Some widgets to test the fixes that had to be done ImGui::SetNextWindowSize(ImVec2(400, 400)); if (ImGui::Begin("Regression tests", nullptr, ImGuiWindowFlags_MenuBar)) { ImGui::TextWrapped("Small issues had to be fixed inside DragFloat (cf TempInputText), InputTextMultiline and BeginMenuBar.\n" "This window is here to test those fixes."); ImGui::Separator(); if (ImGui::BeginMenuBar()) { if (ImGui::BeginMenu("My Menu")) { ImGui::MenuItem("Item 1"); ImGui::EndMenu(); } ImGui::EndMenuBar(); } ImGui::TextWrapped("DragFloat will reuse the Item ID when double clicking. This is allowed via Push/PopAllowDuplicateID"); ImGui::DragFloat("dragf", &f3); ImGui::Separator(); ImGui::TextWrapped("An issue was fixed with the InputTextMultiline vertical scrollbar, which trigerred a duplicate ID warning, which was fixed"); ImGui::InputTextMultiline("multiline", text1, 500); } ImGui::End(); // A window that is populated in several steps should still detect duplicates { ImGui::SetNextWindowSize(ImVec2(400, 200)); ImGui::Begin("Window populated in several steps"); ImGui::TextWrapped("This window is populated between several ImGui::Begin/ImGui::End calls (with the same window name).\n" "Duplicates should be detected anyhow."); ImGui::Text("A first InputText"); ImGui::InputText("TTT", text3, 500); ImGui::End(); ImGui::Begin("Window populated in several steps"); ImGui::Separator(); ImGui::Text("The second InputText below reuses the same ID, \nin a different ImGui::Begin/ImGui::End context \n(but with the same window name)"); ImGui::InputText("TTT", text4, 500); ImGui::End(); } } ```
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I am sorry but this seems too complicated (and not free in term of CPU cost). It seems like either you misunderstood my comment (#7669 (comment)) either my approach has a flaw I didn't envision yet. I will instead implement a proof of concept for my approach, it seems easier than discussing this. |
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This is not a full polished feature but to convey the idea: It's a lazier check and doesn't cover every situation but it's much simpler. I think we can come up with a wrap-around version that work regardless of order and doesn't false detect a single moving item. |
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Ignore previous patch I have found a better solution that works for more cases: It adds two extra int32 read from struct + compare in the hot path, and those new fields are stored nearby to maximize cache line reuse. |
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Since you have investigated this topic in detail, I'd appreciate your feedback on this alternative idea, before we can look into polishing it (better tooltip, opt-out config flag). I wonder if we should instead maybe show a tooltip-like but interactive window in the corner, with a link to the FAQ (now that we have links) and a button to disable all. The uttermost reason what I have not implemented this before is the following: |
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Moving this to a branch master...features/debug_conflicting_id with further improvements. |
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Many thanks for taking the time to review this and for providing a better alternative! I really do think this will be a net positive for ImGui users, especially for new users. You are right that your version is less costly. I had not thought of using I checked out your branch, and thoroughly checked the entire ImGui demo, as well as all tools windows (Metrics, ID Stack tool, etc.) in search for potential warnings, and it seems that all warnings were successfully removed.The regressions I had identified withing TempInputText() / Menu / TextInputMultiLine are also OK. Items with duplicate ID created inside distinct calls to `Begin("SameName") / End()" are also correctly detected Some potential typos in your branch: imgui.h, line 2272: // - Code should use ##/### syntax or PushID()/PopID() to make // ==> "to make IDs unique"?imgui.cpp / EndFrame() Now, to address your concerns:
I had tried it. Based on my tests, opening a new window when a widget is hovered, and opening it far away from the mouse cursor it easy to visually miss: a user may see this window long after hovering the widget, and wonder why it is here.
IMHO, this a why a tooltip is perhaps less annoying than an interactive window. Perhaps, adding more red on "This is a programmer error" could convince more developers to correct it before shipping. Something like:
(I just lerped more red into the text color) |
It was intentional because only unclipped items are tested, which makes the cost near invisible and for what it does pretty much solves enough of the problem anyway. I changed it to "%d visible items ..." it seem adequate and less misleading.
Right. I ended up using a shortcut to link to the FAQ. It seems like a good workaround for this. I also added this feature directly in the Tools menu (I've been thinking adding a link to your manual there too). Pushed some tweaks. |
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I will eagerly push it now AND enable it by default as a way to enforce feedback :) I only had to run the |
Also #74, #96, #480, #501, #647, #654, #719, #843, #894, #1057, #1173, #1390, #1414, #1556, #1768, #2041, #2116, #2330, #2475, #2562, #2667, #2807, #2885, #3102, #3375, #3526, #3964, #4008, #4070, #4158, #4172, #4199, #4375, #4395, #4471, #4548, #4612, #4631, #4657, #4796, #5210, #5303, #5360, #5393, #5533, #5692, #5707, #5729, #5773, #5787, #5884, #6046, #6093, #6186, #6223, #6364, #6387, #6567, #6692, #6724, #6939, #6984, #7246, #7270, #7375, #7421, #7434, #7472, #7581, #7724, #7926, #7937 and probably more.. Tagging to increase visibility!
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Merged as 67cd4ea. Tagging 60+ past issues :) |
Good news!
Actually I had done the same with my previous hackish implementation in Dear ImGui Bundle. An old time user (quite familiar with ImGui indeed), was greeted with the warning and actually thanked me. I'll replace it with yours.
I would be pleased. This made me think I should update it. It is now based on ImGui v1.91.1 |
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PS: as far as the last demo code is concerned a possible fix could be: bool reordering = false; // added this
for (int n = 0; n < IM_ARRAYSIZE(item_names); n++)
{
ImGui::PushItemFlag(ImGuiItemFlags_AllowDuplicateId, reordering); // added this
const char* item = item_names[n];
ImGui::Selectable(item);
if (ImGui::IsItemActive() && !ImGui::IsItemHovered())
{
int n_next = n + (ImGui::GetMouseDragDelta(0).y < 0.f ? -1 : 1);
if (n_next >= 0 && n_next < IM_ARRAYSIZE(item_names))
{
item_names[n] = item_names[n_next];
item_names[n_next] = item;
ImGui::ResetMouseDragDelta();
reordering = true; // added this
}
}
ImGui::PopItemFlag(); // added this
}However, since this is intended to be a "simple" version for Drag a Drop, this addition does defeat a little the purpose of being simple. Since the warning is barely visible for only one frame, I'd say it is OK to keep it unchanged, waiting for a future better alternative. |
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Thank you for updating manual!
I have added a similar code in my commit: if (ImGui::TreeNode("Drag to reorder items (simple)"))
{
// FIXME: there is temporary (usually single-frame) ID Conflict during reordering as a same item may be submitting twice.
// This code was always slightly faulty but in a way which was not easily noticeable.
// Until we fix this, enable ImGuiItemFlags_AllowDuplicateId to disable detecting the issue.
ImGui::PushItemFlag(ImGuiItemFlags_AllowDuplicateId, true);Added section in Wiki: |
(fix for #7669)
There is a common user issue which is that developers may reuse the same ID, and will not understand why their widget is not responsive.
This PR will:
View from 10,000 feet
and
This distinction was applied to several widgets inside imgui_widgets.cpp which now call ReserveUniqueID instead of GetID,
when their intention is to reserve a unique ID for the widget.
For grepability, most of the changes are highlighted with a comment
// TRKID.The only changes which are not marked with this are where GetID() was simply replace by ReserveUniqueID() inside imgui_widgets.cpp
These
// TRKIDcomments should be removed before merging, and they are only here to help reviewing the changes.The full
ImGui::ShowDemoWindow()was reviewed to make sure that no duplicated ID was used.Very few changes were required, and they are detailed in the PR.
The tooltip will look like this
5.See this video for a quick overview of the feature and how it is implemented:
https://traineq.org/ImGui/ImGui_PR_Warn_reuse_ID_Explanation.mp4
Summary of changes
struct ImGuiContext: added fields UidIXXX (UidsThisFrame & co)
Inside imgui_internal.h / struct ImGuiContext
struct ImGuiWindow: added ReserveUniqueID(), beside GetID()
imgui_internal.h / near GetID() existing methods
Added PushAllowDuplicateID / PopAllowDuplicateID
imgui_internal.h / near related ID functions (SetActiveID, GetIDWithSeed, ...)
... IMGUI_API void PushAllowDuplicateID(); // Disables the tooltip warning when duplicate IDs are detected. IMGUI_API void PopAllowDuplicateID(); // Re-enables the tooltip warning when duplicate IDs are detected. ...imgui.cpp:3873 / near ReserveUniqueID() implementation
Main logic: ImGui::EndFrame(), NewFrame() and ImGuiWindow::ReserveUniqueID()
ImGui::NewFrame():
... g.UidsThisFrame.resize(0); // Empty the list of items, but keep its allocated data g.UidWasTipDisplayed = false;ImGui::EndFrame():
ImGuiWindow::ReserveUniqueID()
in imgui.cpp, at the end of "[SECTION] ID STACK".
The pseudocode below summarizes its behavior:
imgui_widgets.cpp
Use ReserveUniqueID, allow duplicates when needed (TempInputText, BeginMenuEx)
I went through all the usages of window->GetID() and changed them to ReserveUniqueID when it was possible / desirable.
Places with one-line changes
In all the places below, the change was extremely simple: I simply replaced
window->GetIDbywindow->ReserveUniqueID.For example, in ImGui::ButtonEx
Below is the list of all function where this simple change was applied:
InvisibleButton ArrowButtonEx ImageButton (both versions) Checkbox RadioButton BeginCombo DragScalar SliderScalar VSliderScalar InputTextEx ColorButton CollapsingHeader Selectable PlotEx BeginTabBar TextLink TreeNode(const char *) TreeNodeEx(const char *) TreeNodeExV(const char *)Places where duplicates are needed
TempInputText
TempInputText create text input in place of another active widget (e.g. used when doing a CTRL+Click on drag/slider widgets).
It reuses the widget ID, so we allow it temporarily via PushAllowDuplicateID / PopAllowDuplicateID
GetWindowScrollbarID
GetWindowScrollbarID had to be split in two: ReserveWindowScrollbarID will perform the ID reservation, while GetWindowScrollbarID is only a query.
Luckily, this is the only instance where this was required.
BeginMenuEx
In BeginMenuEx, we initially call GetID() instead of ReserveUniqueID() because were are not "consuming" this ID:
instead, we are only querying IsPopupOpen().
The ID will be consumed later by calling ImGui::PushID(label) + Selectable("") (which will lead to the same ID)
Places with no changes, but worth mentioning
TreeNode(const void *): unchanged
TreeNode(const void* ptr_id)andTreeNodeExV(const void *)are the only instances which callwindow->GetID(const void *).As a consequence, they cannot use the unique id mechanism, but I think their usage is rare enough that is not a big concern.
ImGui::TabBarCalcTabID: unchanged
It still uses window->GetID, to avoid issues when merging with the docking branch.
BeginChild, BeginPopup and co are unchanged:
since they use ImGui::Begin()/End() internally), I suspect they might be called multiple times with the same string,
since it is allowed with ImGui::Begin/End.
imgui_demo.cpp: some minor changes
I went through the full demo Window to look for instances where a duplicate ID might be used, and corrected them.
Very few changes were required:
(for one frame only: see comments in the code)
Demo code in order to test this PR
Add and call this function in any imgui example. This code will trigger the warnings for duplicated IDs,
and will also enable to make sure that the fixes that had to be done are OK.