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Comments, FAQ
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omar
61
imgui.cpp
61
imgui.cpp
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- FREQUENTLY ASKED QUESTIONS (FAQ), TIPS
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- How can I tell whether to dispatch mouse/keyboard to imgui or to my application?
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- How can I display an image? What is ImTextureID, how does it works?
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- How can I have multiple widgets with the same label? Can I have widget without a label? (Yes). A primer on labels and the ID stack.
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- How can I have multiple widgets with the same label or without a label? A primer on labels and the ID Stack.
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- How can I load a different font than the default?
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- How can I easily use icons in my application?
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- How can I load multiple fonts?
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@ -433,63 +433,66 @@
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It could be an identifier to your OpenGL texture (cast GLuint to void*), a pointer to your custom engine material (cast MyMaterial* to void*), etc.
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At the end of the chain, your renderer takes this void* to cast it back into whatever it needs to select a current texture to render.
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Refer to examples applications, where each renderer (in a imgui_impl_xxxx.cpp file) is treating ImTextureID as a different thing.
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(c++ tip: OpenGL uses integers to identify textures. You can safely store an integer into a void*, just cast it to void*, don't take it's address!)
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(C++ tip: OpenGL uses integers to identify textures. You can safely store an integer into a void*, just cast it to void*, don't take it's address!)
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To display a custom image/texture within an ImGui window, you may use ImGui::Image(), ImGui::ImageButton(), ImDrawList::AddImage() functions.
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Dear ImGui will generate the geometry and draw calls using the ImTextureID that you passed and which your renderer can use.
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You may call ImGui::ShowMetricsWindow() to explore active draw lists and visualize/understand how the draw data is generated.
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It is your responsibility to get textures uploaded to your GPU.
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Q: Can I have multiple widgets with the same label? Can I have widget without a label?
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A: Yes. A primer on labels and the ID stack...
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Q: How can I have multiple widgets with the same label or without a label?
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A: A primer on labels and the ID Stack...
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- Elements that are typically not clickable, such as Text() items don't need an ID.
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- Interactive widgets require state to be carried over multiple frames (most typically Dear ImGui often needs to remember what is
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the "active" widget). to do so they need a unique ID. unique ID are typically derived from a string label, an integer index or a pointer.
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the "active" widget). To do so they need a unique ID. Unique ID are typically derived from a string label, an integer index or a pointer.
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Button("OK"); // Label = "OK", ID = hash of "OK"
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Button("Cancel"); // Label = "Cancel", ID = hash of "Cancel"
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Button("OK"); // Label = "OK", ID = top of id stack + hash of "OK"
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Button("Cancel"); // Label = "Cancel", ID = top of id stack + hash of "Cancel"
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- ID are uniquely scoped within windows, tree nodes, etc. so no conflict can happen if you have two buttons called "OK"
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in two different windows or in two different locations of a tree.
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- ID are uniquely scoped within windows, tree nodes, etc. which all push to the ID stack. So having two buttons labeled "OK"
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in two different windows or in two different locations of a tree is fine.
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- If you have a same ID twice in the same location, you'll have a conflict:
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Button("OK");
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Button("OK"); // ID collision! Both buttons will be treated as the same.
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Button("OK"); // ID collision! Interacting with either button will trigger the first one.
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Fear not! this is easy to solve and there are many ways to solve it!
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- When passing a label you can optionally specify extra unique ID information within string itself.
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- Solving ID conflict in a simple/local context:
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When passing a label you can optionally specify extra unique ID information within string itself.
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Use "##" to pass a complement to the ID that won't be visible to the end-user.
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This helps solving the simple collision cases when you know which items are going to be created.
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Button("Play"); // Label = "Play", ID = hash of "Play"
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Button("Play##foo1"); // Label = "Play", ID = hash of "Play##foo1" (different from above)
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Button("Play##foo2"); // Label = "Play", ID = hash of "Play##foo2" (different from above)
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Button("Play"); // Label = "Play", ID = top of id stack + hash of "Play"
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Button("Play##foo1"); // Label = "Play", ID = top of id stack + hash of "Play##foo1" (different from above)
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Button("Play##foo2"); // Label = "Play", ID = top of id stack + hash of "Play##foo2" (different from above)
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- If you want to completely hide the label, but still need an ID:
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Checkbox("##On", &b); // Label = "", ID = hash of "##On" (no label!)
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Checkbox("##On", &b); // Label = "", ID = top of id stack + hash of "##On" (no label!)
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- Occasionally/rarely you might want change a label while preserving a constant ID. This allows you to animate labels.
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For example you may want to include varying information in a window title bar, but windows are uniquely identified by their ID..
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Use "###" to pass a label that isn't part of ID:
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Button("Hello###ID"; // Label = "Hello", ID = hash of "ID"
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Button("World###ID"; // Label = "World", ID = hash of "ID" (same as above)
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Button("Hello###ID"; // Label = "Hello", ID = top of id stack + hash of "ID"
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Button("World###ID"; // Label = "World", ID = top of id stack + hash of "ID" (same as above)
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sprintf(buf, "My game (%f FPS)###MyGame", fps);
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Begin(buf); // Variable label, ID = hash of "MyGame"
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- Use PushID() / PopID() to create scopes and avoid ID conflicts within the same Window.
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- Solving ID conflict in a more general manner:
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Use PushID() / PopID() to create scopes and manipulate the ID stack, as to avoid ID conflicts within the same Window.
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This is the most convenient way of distinguishing ID if you are iterating and creating many UI elements.
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You can push a pointer, a string or an integer value. Remember that ID are formed from the concatenation of _everything_ in the ID stack!
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You can push a pointer, a string or an integer value into the ID stack.
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Remember that ID are formed from the concatenation of _everything_ in the ID stack!
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for (int i = 0; i < 100; i++)
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{
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PushID(i);
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Button("Click"); // Label = "Click", ID = hash of integer + "label" (unique)
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Button("Click"); // Label = "Click", ID = top of id stack + hash of integer + hash of "Click"
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PopID();
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}
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@ -497,7 +500,7 @@
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{
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MyObject* obj = Objects[i];
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PushID(obj);
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Button("Click"); // Label = "Click", ID = hash of pointer + "label" (unique)
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Button("Click"); // Label = "Click", ID = top of id stack + hash of pointer + hash of "Click"
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PopID();
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}
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{
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MyObject* obj = Objects[i];
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PushID(obj->Name);
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Button("Click"); // Label = "Click", ID = hash of string + "label" (unique)
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Button("Click"); // Label = "Click", ID = top of id stack + hash of string + hash of "Click"
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PopID();
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}
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- More example showing that you can stack multiple prefixes into the ID stack:
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Button("Click"); // Label = "Click", ID = hash of "Click"
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Button("Click"); // Label = "Click", ID = top of id stack + hash of "Click"
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PushID("node");
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Button("Click"); // Label = "Click", ID = hash of "node" + "Click"
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Button("Click"); // Label = "Click", ID = top of id stack + hash of "node" + hash of "Click"
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PushID(my_ptr);
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Button("Click"); // Label = "Click", ID = hash of "node" + ptr + "Click"
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Button("Click"); // Label = "Click", ID = top of id stack + hash of "node" + hash of ptr + hash of "Click"
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PopID();
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PopID();
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- Tree nodes implicitly creates a scope for you by calling PushID().
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Button("Click"); // Label = "Click", ID = hash of "Click"
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Button("Click"); // Label = "Click", ID = top of id stack + hash of "Click"
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if (TreeNode("node"))
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{
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Button("Click"); // Label = "Click", ID = hash of "node" + "Click"
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Button("Click"); // Label = "Click", ID = top of id stack + hash of "node" + hash of "Click"
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TreePop();
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}
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- When working with trees, ID are used to preserve the open/close state of each tree node.
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Depending on your use cases you may want to use strings, indices or pointers as ID.
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e.g. when displaying a single object that may change over time (dynamic 1-1 relationship), using a static string as ID will preserve your
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e.g. when following a single pointer that may change over time, using a static string as ID will preserve your
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node open/closed state when the targeted 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 differently.
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experiment and see what makes more sense!
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experiment and see what makes more sense in your situation!
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Q: How can I load a different font than the default? (default is an embedded version of ProggyClean.ttf, rendered at size 13)
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A: Use the font atlas to load the TTF/OTF file you want:
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