Resizable panels + right and bottom panels (#438)

* Side panel resizing and add right panels

* Add resizable top/bottom panels

* Deprecate TopPanel

* Final tweaks and update CHANGELOG.md

Author: emilk

CHANGELOG.md

@@ -8,13 +8,20 @@ NOTE: [`eframe`](eframe/CHANGELOG.md), [`egui_web`](egui_web/CHANGELOG.md) and [
 ## Unreleased
 
 ### Added ⭐
+* Add right and bottom panels (`SidePanel::right` and `Panel::bottom`).
+* Add resizable panels.
+* Add an option to overwrite frame of a `Panel`.
 * Add `Style::override_text_style` to easily change the text style of everything in a `Ui` (or globally).
 * You can now change `TextStyle` on checkboxes, radio buttons and `SelectableLabel`.
 * Add support for [cint](https://crates.io/crates/cint) under `cint` feature.
 * Add features `extra_asserts` and `extra_debug_asserts` to enable additional checks.
-* Add an option to overwrite frame of `SidePanel` and `TopPanel`.
 * `TextEdit` now supports edits on a generic buffer using `TextBuffer`.
 
+### Changed 🔧
+* `TopPanel::top` is now `TopBottomPanel::top`.
+* `SidePanel::left` no longet takes the default width by argument, but by a builder call.
+
+
 ## 0.12.0 - 2021-05-10 - Multitouch, user memory, window pivots, and improved plots
 
 ### Added ⭐

egui/src/containers/area.rs

@@ -282,7 +282,7 @@ impl Prepared {
         // (except in rare cases where they don't fit).
         // Adjust clip rect so we don't cast shadows on side panels:
         let central_area = ctx.available_rect();
-        let is_within_central_area = central_area.contains(self.state.pos);
+        let is_within_central_area = central_area.contains_rect(self.state.rect().shrink(1.0));
         if is_within_central_area {
             clip_rect = clip_rect.intersect(central_area);
         }

egui/src/containers/mod.rs

@@ -17,9 +17,12 @@ pub use {
     collapsing_header::*,
     combo_box::*,
     frame::Frame,
-    panel::{CentralPanel, SidePanel, TopPanel},
+    panel::{CentralPanel, SidePanel, TopBottomPanel},
     popup::*,
     resize::Resize,
     scroll_area::ScrollArea,
     window::Window,
 };
+
+#[allow(deprecated)]
+pub use panel::TopPanel;