Add ListClipper wrapper

imgui-examples/examples/test_window_impl.rs

@@ -49,6 +49,7 @@ struct State {
     dont_ask_me_next_time: bool,
     stacked_modals_item: usize,
     stacked_modals_color: [f32; 4],
+    app_log: Vec<String>,
 
     tabs: TabState,
 }
@@ -108,6 +109,7 @@ impl Default for State {
             dont_ask_me_next_time: false,
             stacked_modals_item: 0,
             stacked_modals_color: [0.4, 0.7, 0.0, 0.5],
+            app_log: Vec::new(),
             tabs: TabState::default(),
         }
     }
@@ -312,6 +314,10 @@ fn show_test_window(ui: &Ui, state: &mut State, opened: &mut bool) {
         );
     }
 
+    if state.show_app_log {
+        show_app_log(ui, &mut state.app_log);
+    }
+
     let mut window = Window::new(im_str!("ImGui Demo"))
         .title_bar(!state.no_titlebar)
         .resizable(!state.no_resize)
@@ -1232,3 +1238,56 @@ fn show_example_app_custom_rendering(ui: &Ui, state: &mut CustomRenderingState,
             }
         });
 }
+
+fn show_app_log(ui: &Ui, app_log: &mut Vec<String>) {
+    Window::new(im_str!("Example: Log"))
+        .size([500.0, 400.0], Condition::FirstUseEver)
+        .build(ui, || {
+            if ui.small_button(im_str!("[Debug] Add 5 entries")) {
+                let categories = ["info", "warn", "error"];
+                let words = [
+                    "Bumfuzzled",
+                    "Cattywampus",
+                    "Snickersnee",
+                    "Abibliophobia",
+                    "Absquatulate",
+                    "Nincompoop",
+                    "Pauciloquent",
+                ];
+                for _ in 0..5 {
+                    let category = categories[app_log.len() % categories.len()];
+                    let word = words[app_log.len() % words.len()];
+                    let frame = ui.frame_count();
+                    let time = ui.time();
+                    let text = format!(
+                        "{:05} {} Hello, current time is {:.1}, here's a word: {}",
+                        frame, category, time, word
+                    );
+                    app_log.push(text);
+                }
+            }
+            if ui.button(im_str!("Clear"), [0.0, 0.0]) {
+                app_log.clear();
+            }
+            ui.same_line(0.0);
+            if ui.button(im_str!("Copy"), [0.0, 0.0]) {
+                ui.set_clipboard_text(&ImString::from(app_log.join("\n")));
+            }
+            ui.separator();
+            ChildWindow::new("logwindow")
+                .flags(WindowFlags::HORIZONTAL_SCROLLBAR)
+                .build(ui, || {
+                    let mut clipper = ListClipper::new()
+                        .items_count(app_log.len() as i32)
+                        .begin(ui);
+                    while clipper.step() {
+                        for line in clipper.display_start()..clipper.display_end() {
+                            ui.text(&app_log[line as usize]);
+                        }
+                    }
+                    if ui.scroll_y() >= ui.scroll_max_y() {
+                        ui.set_scroll_here_y();
+                    }
+                });
+        });
+}

imgui/src/lib.rs

@@ -23,6 +23,7 @@ pub use self::input_widget::{
 pub use self::io::*;
 pub use self::layout::*;
 pub use self::legacy::*;
+pub use self::list_clipper::ListClipper;
 pub use self::plothistogram::PlotHistogram;
 pub use self::plotlines::PlotLines;
 pub use self::popup_modal::PopupModal;
@@ -58,6 +59,7 @@ pub mod internal;
 mod io;
 mod layout;
 mod legacy;
+mod list_clipper;
 mod plothistogram;
 mod plotlines;
 mod popup_modal;

imgui/src/list_clipper.rs

@@ -0,0 +1,82 @@
+use std::marker::PhantomData;
+use std::thread;
+
+use crate::sys;
+use crate::Ui;
+
+pub struct ListClipper {
+    items_count: i32,
+    items_height: f32,
+}
+
+impl ListClipper {
+    pub fn new() -> Self {
+        ListClipper {
+            items_count: -1,
+            items_height: -1.0,
+        }
+    }
+
+    pub fn items_count(mut self, items_count: i32) -> Self {
+        self.items_count = items_count;
+        self
+    }
+
+    pub fn items_height(mut self, items_height: f32) -> Self {
+        self.items_height = items_height;
+        self
+    }
+
+    pub fn begin<'ui>(self, ui: &Ui<'ui>) -> ListClipperToken<'ui> {
+        let list_clipper = unsafe {
+            let list_clipper = sys::ImGuiListClipper_ImGuiListClipper();
+            sys::ImGuiListClipper_Begin(list_clipper, self.items_count, self.items_height);
+            list_clipper
+        };
+        ListClipperToken::new(ui, list_clipper)
+    }
+}
+
+pub struct ListClipperToken<'ui> {
+    list_clipper: *mut sys::ImGuiListClipper,
+    _phantom: PhantomData<&'ui Ui<'ui>>,
+}
+
+impl<'ui> ListClipperToken<'ui> {
+    fn new(_: &Ui<'ui>, list_clipper: *mut sys::ImGuiListClipper) -> Self {
+        Self {
+            list_clipper,
+            _phantom: PhantomData,
+        }
+    }
+
+    pub fn step(&mut self) -> bool {
+        unsafe { sys::ImGuiListClipper_Step(self.list_clipper) }
+    }
+
+    pub fn end(&mut self) {
+        unsafe {
+            sys::ImGuiListClipper_End(self.list_clipper);
+        }
+    }
+
+    pub fn display_start(&self) -> i32 {
+        unsafe { (*self.list_clipper).DisplayStart }
+    }
+
+    pub fn display_end(&self) -> i32 {
+        unsafe { (*self.list_clipper).DisplayEnd }
+    }
+}
+
+impl<'ui> Drop for ListClipperToken<'ui> {
+    fn drop(&mut self) {
+        if !self.step() {
+            unsafe {
+                sys::ImGuiListClipper_destroy(self.list_clipper);
+            };
+        } else if !thread::panicking() {
+            panic!("step() was not called until it returned false");
+        }
+    }
+}