Merge pull request #468 from AngelOfSol/feature/build-return

Modifies build functions to allow returning data from the build closures. Thanks @AngelOfSol !

CHANGELOG.markdown

@@ -2,6 +2,9 @@
 
 ## [Unreleased]
 
+- BREAKING: Modifies `build` style methods to allow the provide closure to return a value.  The build call will then return Some(value) if the closure is called, and None if it isn't.
+ - The most likely breaking changes users will see is that they will need to add semicolons after calling `build`, because these function no longer return `()`.
+
 - BREAKING: Created `with_x` variants for most functions which previously took multiple parameters where some had default arguments in the C++. This makes calling most functions simpler and more similar to the C++.
  - The most likely breaking changes users will see is `button` and `same_line` now take one fewer parameter -- if you were calling `button` with `[0.0, 0.0]`, simply delete that -- otherwise, call `button_with_size`. Similarly, for `same_line`, if you were passing in `0.0.` simply delete that parameter. Otherwise, call `same_line_with_pos`.
 

imgui-examples/examples/test_window_impl.rs

@@ -828,7 +828,7 @@ CTRL+click on individual component to input value.\n",
                 });
             });
         }
-    })
+    });
 }
 
 fn show_example_app_main_menu_bar<'a>(ui: &Ui<'a>, state: &mut State) {
@@ -942,7 +942,7 @@ output your content because that would create a feedback loop.",
             for i in 0..state.lines {
                 ui.text(format!("{:2$}This is line {}", "", i, i as usize * 4));
             }
-        })
+        });
 }
 
 fn show_example_app_fixed_overlay(ui: &Ui, opened: &mut bool) {

imgui/src/popups.rs

@@ -125,11 +125,10 @@ impl<'p> PopupModal<'p> {
     }
 
     /// Consume and draw the PopupModal.
+    /// Returns the result of the closure, if it is called.
     #[doc(alias = "BeginPopupModal")]
-    pub fn build<F: FnOnce()>(self, ui: &Ui<'_>, f: F) {
-        if let Some(_popup) = self.begin_popup(ui) {
-            f();
-        }
+    pub fn build<T, F: FnOnce() -> T>(self, ui: &Ui<'_>, f: F) -> Option<T> {
+        self.begin_popup(ui).map(|_popup| f())
     }
 
     /// Consume and draw the PopupModal.

imgui/src/widget/combo_box.rs

@@ -155,12 +155,11 @@ impl<'a> ComboBox<'a> {
         }
     }
     /// Creates a combo box and runs a closure to construct the popup contents.
+    /// Returns the result of the closure, if it is called.
     ///
     /// Note: the closure is not called if the combo box is not open.
-    pub fn build<F: FnOnce()>(self, ui: &Ui, f: F) {
-        if let Some(_combo) = self.begin(ui) {
-            f();
-        }
+    pub fn build<T, F: FnOnce() -> T>(self, ui: &Ui, f: F) -> Option<T> {
+        self.begin(ui).map(|_combo| f())
     }
 }
 

imgui/src/widget/list_box.rs

@@ -49,12 +49,11 @@ impl<'a> ListBox<'a> {
         }
     }
     /// Creates a list box and runs a closure to construct the list contents.
+    /// Returns the result of the closure, if it is called.
     ///
     /// Note: the closure is not called if the list box is not open.
-    pub fn build<F: FnOnce()>(self, ui: &Ui, f: F) {
-        if let Some(_list) = self.begin(ui) {
-            f();
-        }
+    pub fn build<T, F: FnOnce() -> T>(self, ui: &Ui<'_>, f: F) -> Option<T> {
+        self.begin(ui).map(|_list| f())
     }
 }
 

imgui/src/widget/tab.rs

@@ -103,12 +103,11 @@ impl<'a> TabBar<'a> {
     }
 
     /// Creates a tab bar and runs a closure to construct the contents.
+    /// Returns the result of the closure, if it is called.
     ///
     /// Note: the closure is not called if no tabbar content is visible
-    pub fn build<F: FnOnce()>(self, ui: &Ui, f: F) {
-        if let Some(_tab) = self.begin(ui) {
-            f();
-        }
+    pub fn build<T, F: FnOnce() -> T>(self, ui: &Ui<'_>, f: F) -> Option<T> {
+        self.begin(ui).map(|_tab| f())
     }
 }
 
@@ -175,12 +174,11 @@ impl<'a> TabItem<'a> {
     }
 
     /// Creates a tab item and runs a closure to construct the contents.
+    /// Returns the result of the closure, if it is called.
     ///
     /// Note: the closure is not called if the tab item is not selected
-    pub fn build<F: FnOnce()>(self, ui: &Ui, f: F) {
-        if let Some(_tab) = self.begin(ui) {
-            f();
-        }
+    pub fn build<T, F: FnOnce() -> T>(self, ui: &Ui<'_>, f: F) -> Option<T> {
+        self.begin(ui).map(|_tab| f())
     }
 }
 

imgui/src/widget/tree.rs

@@ -264,12 +264,11 @@ impl<'a> TreeNode<'a> {
         }
     }
     /// Creates a tree node and runs a closure to construct the contents.
+    /// Returns the result of the closure, if it is called.
     ///
     /// Note: the closure is not called if the tree node is not open.
-    pub fn build<F: FnOnce()>(self, ui: &Ui, f: F) {
-        if let Some(_node) = self.push(ui) {
-            f();
-        }
+    pub fn build<T, F: FnOnce() -> T>(self, ui: &Ui<'_>, f: F) -> Option<T> {
+        self.push(ui).map(|_node| f())
     }
 }
 

imgui/src/window/child_window.rs

@@ -277,13 +277,12 @@ impl<'a> ChildWindow<'a> {
         }
     }
     /// Creates a child window and runs a closure to construct the contents.
+    /// Returns the result of the closure, if it is called.
     ///
     /// Note: the closure is not called if no window content is visible (e.g. window is collapsed
     /// or fully clipped).
-    pub fn build<F: FnOnce()>(self, ui: &Ui, f: F) {
-        if let Some(_window) = self.begin(ui) {
-            f();
-        }
+    pub fn build<T, F: FnOnce() -> T>(self, ui: &Ui<'_>, f: F) -> Option<T> {
+        self.begin(ui).map(|_window| f())
     }
 }
 

imgui/src/window/mod.rs

@@ -541,13 +541,12 @@ impl<'a> Window<'a> {
         }
     }
     /// Creates a window and runs a closure to construct the contents.
+    /// Returns the result of the closure, if it is called.
     ///
     /// Note: the closure is not called if no window content is visible (e.g. window is collapsed
     /// or fully clipped).
-    pub fn build<F: FnOnce()>(self, ui: &Ui, f: F) {
-        if let Some(_window) = self.begin(ui) {
-            f();
-        }
+    pub fn build<T, F: FnOnce() -> T>(self, ui: &Ui<'_>, f: F) -> Option<T> {
+        self.begin(ui).map(|_window| f())
     }
 }