Style: added PushStyleVarX(), PushStyleVarY() helpers to modify only one component of a ImVec2 var.

+ tweak existing function to early out on error.

docs/CHANGELOG.txt

@@ -56,7 +56,8 @@ Other changes:
 - InputText: allow callback to update buffer while in read-only mode. (imgui_club/#46)
 - InputText: fixed an issue programmatically refocusing a multi-line input which was just active. (#4761, #7870)
 - TextLink(), TextLinkOpenURL(): change mouse cursor to Hand shape when hovered. (#7885, #7660)
-- Fonts: Made it possible to use PushFont()/PopFont() calls accross Begin() calls. (#3224, #3875, #6398, #7903)
+- Style: added PushStyleVarX(), PushStyleVarY() helpers to modify only one component of a ImVec2 var.
+- Fonts: made it possible to use PushFont()/PopFont() calls accross Begin() calls. (#3224, #3875, #6398, #7903)
 - Backends: GLFW: added ImGui_ImplGlfw_Sleep() helper function because GLFW does not
   provide a way to do a portable sleep. (#7844)
 - Backends: SDL2, SDL3: ignore events of other SDL windows. (#7853) [@madebr, @ocornut]

docs/TODO.txt

@@ -194,7 +194,6 @@ It's mostly a bunch of personal notes, probably incomplete. Feel free to query i
  - settings/persistence: helpers to make TreeNodeBehavior persist (even during dev!) - may need to store some semantic and/or data type in ImGuiStoragePair
 
  - style: better default styles. (#707)
- - style: PushStyleVar: allow direct access to individual float X/Y elements.
  - style: add a highlighted text color (for headers, etc.)
  - style: border types: out-screen, in-screen, etc. (#447)
  - style: add window shadow (fading away from the window. Paint-style calculation of vertices alpha after drawlist would be easier)

imgui.cpp

@@ -3309,28 +3309,56 @@ void ImGui::PushStyleVar(ImGuiStyleVar idx, float val)
 {
     ImGuiContext& g = *GImGui;
     const ImGuiDataVarInfo* var_info = GetStyleVarInfo(idx);
-    if (var_info->Type == ImGuiDataType_Float && var_info->Count == 1)
+    if (var_info->Type != ImGuiDataType_Float || var_info->Count != 1)
     {
-        float* pvar = (float*)var_info->GetVarPtr(&g.Style);
-        g.StyleVarStack.push_back(ImGuiStyleMod(idx, *pvar));
-        *pvar = val;
+        IM_ASSERT_USER_ERROR(0, "Calling PushStyleVar() variant with wrong type!");
         return;
     }
-    IM_ASSERT_USER_ERROR(0, "Calling PushStyleVar() variant with wrong type!");
+    float* pvar = (float*)var_info->GetVarPtr(&g.Style);
+    g.StyleVarStack.push_back(ImGuiStyleMod(idx, *pvar));
+    *pvar = val;
+}
+
+void ImGui::PushStyleVarX(ImGuiStyleVar idx, float val_x)
+{
+    ImGuiContext& g = *GImGui;
+    const ImGuiDataVarInfo* var_info = GetStyleVarInfo(idx);
+    if (var_info->Type != ImGuiDataType_Float || var_info->Count != 2)
+    {
+        IM_ASSERT_USER_ERROR(0, "Calling PushStyleVar() variant with wrong type!");
+        return;
+    }
+    ImVec2* pvar = (ImVec2*)var_info->GetVarPtr(&g.Style);
+    g.StyleVarStack.push_back(ImGuiStyleMod(idx, *pvar));
+    pvar->x = val_x;
+}
+
+void ImGui::PushStyleVarY(ImGuiStyleVar idx, float val_y)
+{
+    ImGuiContext& g = *GImGui;
+    const ImGuiDataVarInfo* var_info = GetStyleVarInfo(idx);
+    if (var_info->Type != ImGuiDataType_Float || var_info->Count != 2)
+    {
+        IM_ASSERT_USER_ERROR(0, "Calling PushStyleVar() variant with wrong type!");
+        return;
+    }
+    ImVec2* pvar = (ImVec2*)var_info->GetVarPtr(&g.Style);
+    g.StyleVarStack.push_back(ImGuiStyleMod(idx, *pvar));
+    pvar->y = val_y;
 }
 
 void ImGui::PushStyleVar(ImGuiStyleVar idx, const ImVec2& val)
 {
     ImGuiContext& g = *GImGui;
     const ImGuiDataVarInfo* var_info = GetStyleVarInfo(idx);
-    if (var_info->Type == ImGuiDataType_Float && var_info->Count == 2)
+    if (var_info->Type != ImGuiDataType_Float || var_info->Count != 2)
     {
-        ImVec2* pvar = (ImVec2*)var_info->GetVarPtr(&g.Style);
-        g.StyleVarStack.push_back(ImGuiStyleMod(idx, *pvar));
-        *pvar = val;
+        IM_ASSERT_USER_ERROR(0, "Calling PushStyleVar() variant with wrong type!");
         return;
     }
-    IM_ASSERT_USER_ERROR(0, "Calling PushStyleVar() variant with wrong type!");
+    ImVec2* pvar = (ImVec2*)var_info->GetVarPtr(&g.Style);
+    g.StyleVarStack.push_back(ImGuiStyleMod(idx, *pvar));
+    *pvar = val;