From 4c7b7881c84eb83f2fcff11cff5ba41fc5a615d4 Mon Sep 17 00:00:00 2001
From: Huang Xin <chrox.huang@gmail.com>
Date: Sun, 23 Feb 2025 15:56:00 +0100
Subject: [PATCH] feat: add d/u shortcuts for half page navigation, closes #62
 (#437)

---
 .../src/app/reader/hooks/useBookShortcuts.ts   | 18 ++++++++++++++++++
 apps/readest-app/src/helpers/shortcuts.ts      |  6 +++++-
 apps/readest-app/src/types/view.ts             |  4 ++--
 3 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/apps/readest-app/src/app/reader/hooks/useBookShortcuts.ts b/apps/readest-app/src/app/reader/hooks/useBookShortcuts.ts
index 2c5779fa..a4b5fe2f 100644
--- a/apps/readest-app/src/app/reader/hooks/useBookShortcuts.ts
+++ b/apps/readest-app/src/app/reader/hooks/useBookShortcuts.ts
@@ -61,6 +61,22 @@ const useBookShortcuts = ({ sideBarBookKey, bookKeys }: UseBookShortcutsProps) =
     getView(sideBarBookKey)?.history.back();
   };
 
+  const goHalfPageDown = () => {
+    const view = getView(sideBarBookKey);
+    const viewSettings = getViewSettings(sideBarBookKey ?? '');
+    if (view && viewSettings && viewSettings.scrolled) {
+      view.next(view.renderer.size / 2);
+    }
+  };
+
+  const goHalfPageUp = () => {
+    const view = getView(sideBarBookKey);
+    const viewSettings = getViewSettings(sideBarBookKey ?? '');
+    if (view && viewSettings && viewSettings.scrolled) {
+      view.prev(view.renderer.size / 2);
+    }
+  };
+
   const goForward = () => {
     getView(sideBarBookKey)?.history.forward();
   };
@@ -123,6 +139,8 @@ const useBookShortcuts = ({ sideBarBookKey, bookKeys }: UseBookShortcutsProps) =
       onGoRight: goRight,
       onGoPrev: goPrev,
       onGoNext: goNext,
+      onGoHalfPageDown: goHalfPageDown,
+      onGoHalfPageUp: goHalfPageUp,
       onGoBack: goBack,
       onGoForward: goForward,
       onZoomIn: zoomIn,
diff --git a/apps/readest-app/src/helpers/shortcuts.ts b/apps/readest-app/src/helpers/shortcuts.ts
index 79c45172..0a7e1a67 100644
--- a/apps/readest-app/src/helpers/shortcuts.ts
+++ b/apps/readest-app/src/helpers/shortcuts.ts
@@ -11,6 +11,8 @@ export interface ShortcutConfig {
   onGoRight: string[];
   onGoNext: string[];
   onGoPrev: string[];
+  onGoHalfPageDown: string[];
+  onGoHalfPageUp: string[];
   onGoBack: string[];
   onGoForward: string[];
   onZoomIn: string[];
@@ -33,13 +35,15 @@ const DEFAULT_SHORTCUTS: ShortcutConfig = {
   onGoRight: ['ArrowRight', 'PageDown', 'l', ' '],
   onGoNext: ['ArrowDown', 'j'],
   onGoPrev: ['ArrowUp', 'k'],
+  onGoHalfPageDown: ['shift+ArrowDown', 'd'],
+  onGoHalfPageUp: ['shift+ArrowUp', 'u'],
   onGoBack: ['shift+ArrowLeft', 'shift+h'],
   onGoForward: ['shift+ArrowRight', 'shift+l'],
   onZoomIn: ['ctrl+=', 'cmd+=', 'shift+='],
   onZoomOut: ['ctrl+-', 'cmd+-', 'shift+-'],
   onResetZoom: ['ctrl+0', 'cmd+0'],
   onSaveNote: ['ctrl+Enter'],
-  onCloseNote: ['Escape']
+  onCloseNote: ['Escape'],
 };
 
 // Load shortcuts from localStorage or fallback to defaults
diff --git a/apps/readest-app/src/types/view.ts b/apps/readest-app/src/types/view.ts
index 01226636..34f5abf6 100644
--- a/apps/readest-app/src/types/view.ts
+++ b/apps/readest-app/src/types/view.ts
@@ -36,8 +36,8 @@ export interface FoliateView extends HTMLElement {
   };
   renderer: {
     scrolled?: boolean;
-    size: number;
-    viewSize: number;
+    size: number; // current page height
+    viewSize: number; // whole document view height
     start: number;
     end: number;
     setAttribute: (name: string, value: string | number) => void;