IME input problem.

[urjskhzk]

Version/Branch of Dear ImGui:

Version: 1.84.2
Branch: master

Back-end/Renderer/Compiler/OS

Back-ends: win32 dx9
Compiler: vs2019
Operating System: Windows 10

My Issue/Question:

This is a case when WM_CHAR and WM_LBUTTONDOWN events occur at the same time.

io.MouseDown[0]: true
io.InputQueueCharacters: Size 1, Data 44032 '가'

1. Good

static bool b = false;
static char buf[256] = { 0, };
ImGui::Begin("Hello, world!");
ImGui::InputText("InputText", buf, _countof(buf));
ImGui::Checkbox("Checkbox", &b);
ImGui::End();

2. Bad

static bool b = false;
static char buf[256] = { 0, };
ImGui::Begin("Hello, world!");
ImGui::Checkbox("Checkbox", &b);
ImGui::InputText("InputText", buf, _countof(buf));
ImGui::End();

3. A is Good / B is Bad

static char buf1[36] = { 0, };
static char buf2[36] = { 0, };
ImGui::Begin("Hello, world!");
ImGui::InputText("A", buf1, _countof(buf1));
ImGui::InputText("B", buf2, _countof(buf2));
ImGui::End();

Screenshots/Video

Standalone, minimal, complete and verifiable example:

[ocornut]

This is not an IME specific problem but an IME triggering both events simultaneously would exacerbate the problem.

If you use a custom input queue like https://gist.github.com/ocornut/8417344f3506790304742b07887adf9f you can problably work around this problem. We are now working (well, thedmd is) on an official version of this to be in master.

[ocornut]

I assume that the click on checkbox makes the IME flush the unsubmitted text and send both events? Can you confirm that the WM_CHAR event is always sent before WM_LBUTTONDOWN ?

[urjskhzk]

This is a situation that occurs frequently in the Korean input process.
I don't know about Chinese and Japanese input.

'R' is 'ㄱ' and 'K' is 'ㅏ'.

[urjskhzk]

[LunaTheFoxgirl]

Can confirm that the problem also happens with Japanese IME and in some cases (due to the SDL2 backend Inochi Creator is using) can cause crashes due to cut-off UTF8 sequences.
Though I think it's a bit of a multi-fold problem in our case.

[ocornut]

Hello,

Was looking into this day.
AFAIK this should be fixed by 1.87 event queue with a conforming backend (#4921) since text input trickles when preceded by a mouse down on same frame.

However, I can't repro (with io.ConfigInputTrickleEventQueue = false;) before with my IME showing a suggestion window, the first click is inhibited by win32 popup logic and I don't get the mouse down. However pretty sure it would now handle it properly with 1.87, but let me know if it doesn't!

[ocornut]

PS: In the very last commit in Tools>DebugLog I have added a [X] IO checkbox allowing to visualize input events and how they are trickled.