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Added FAQ/comments
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imgui.cpp
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imgui.cpp
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3/ ImGui::Render() to render all the accumulated command-lists. it will call your RenderDrawListFn handler that you set in the IO structure.
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- all rendering information are stored into command-lists until ImGui::Render() is called.
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- effectively it means you can create widgets at any time in your code, regardless of "update" vs "render" considerations.
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- refer to the examples applications in the examples/ folder for instruction on how to setup your code.
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- a typical application skeleton may be:
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// Application init
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// TODO: Fill all 'Settings' fields of the io structure
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// TODO: Fill all settings fields of the io structure
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ImGuiIO& io = ImGui::GetIO();
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io.DisplaySize.x = 1920.0f;
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io.DisplaySize.y = 1280.0f;
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@ -87,14 +88,33 @@
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// swap video buffer, etc.
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}
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TROUBLESHOOTING & FREQUENTLY ASKED QUESTIONS
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- if text or lines are blurry when integrating ImGui in your engine:
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- in your Render function, try translating your projection matrix by (0.5f,0.5f) or (0.375f,0.375f)
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- try adjusting ImGui::GetIO().PixelCenterOffset to 0.5f or 0.375f
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- some widgets carry state and requires an unique ID to do so.
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- unique ID are typically derived from a string label, an indice or a pointer.
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- use PushID/PopID to easily create scopes and avoid ID conflicts. A Window is also an implicit scope.
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- when creating trees, ID are particularly important because you want to preserve the opened/closed state of tree nodes.
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- if you can only see text but no solid shapes or lines:
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- make sure io.FontTexUvForWhite is set to the texture coordinates of a pure white pixel in your texture.
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(this is done for you if you are using the default font)
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(ImGui is using this texture coordinate to draw solid objects so text and solid draw calls can be merged into one.)
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- if you want to use a different font than the default:
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- create bitmap font data using BMFont, make sure that BMFont is exporting the .fnt file in Binary mode.
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io.Font = new ImBitmapFont();
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io.Font->LoadFromFile("path_to_your_fnt_file.fnt");
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- load your texture yourself. texture *MUST* have white pixel at UV coordinate io.FontTexUvForWhite. This is used to draw all solid shapes.
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- the extra_fonts/ folder provides examples of using external fonts.
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- if you are confused about the meaning or use of ID in ImGui:
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- some widgets requires state to be carried over multiple frames (most typically ImGui often wants remember what is the "active" widget).
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to do so they need an unique ID. unique ID are typically derived from a string label, an indice or a pointer.
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when you call Button("OK") the button shows "OK" and also use "OK" as an ID.
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- ID are uniquely scoped within Windows so no conflict can happen if you have two buttons called "OK" in two different Windows.
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within a same Window, use PushID() / PopID() to easily create scopes and avoid ID conflicts.
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so if you have a loop creating "multiple" items, you can use PushID() / PopID() with the index of each item, or their pointer, etc.
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some functions like TreeNode() implicitly creates a scope for you by calling PushID()
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- when dealing with trees, ID are important because you want to preserve the opened/closed state of tree nodes.
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depending on your use cases you may want to use strings, indices or pointers as ID. experiment and see what makes more sense!
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e.g. When displaying a single object, using a static string as ID will preserve your node open/closed state when the targetted object change
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e.g. When displaying a list of objects, using indices or pointers as ID will preserve the node open/closed state per object
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@ -102,14 +122,12 @@
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e.g. "Label" display "Label" and uses "Label" as ID
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e.g. "Label##Foobar" display "Label" and uses "Label##Foobar" as ID
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e.g. "##Foobar" display an empty label and uses "##Foobar" as ID
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- if you want to use a different font than the default
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- create bitmap font data using BMFont. allocate ImGui::GetIO().Font and use ->LoadFromFile()/LoadFromMemory().
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- load your texture yourself. texture *MUST* have white pixel at UV coordinate ImGui::GetIO().FontTexUvForWhite. This is used to draw all solid shapes.
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- read articles about the imgui principles (see web links) to understand the requirement and use of ID.
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- tip: the construct 'if (IMGUI_ONCE_UPON_A_FRAME)' will evaluate to true only once a frame, you can use it to add custom UI in the middle of a deep nested inner loop in your code.
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- tip: you can call Render() multiple times (e.g for VR renders), up to you to communicate the extra state to your RenderDrawListFn function.
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- tip: you can create widgets without a Begin/End block, they will go in an implicit window called "Debug"
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- tip: you can create widgets without a Begin()/End() block, they will go in an implicit window called "Debug"
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- tip: read the ShowTestWindow() code for more example of how to use ImGui!
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ISSUES AND TODO-LIST
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