From 70f096abc4c765ad45cfa2997dd25365b5ad5ac0 Mon Sep 17 00:00:00 2001
From: Ritchie Cunningham <ritchie@ritchiecunningham.co.uk>
Date: Sat, 20 Sep 2025 15:51:55 +0100
Subject: [PATCH] [Add] Bound-checked terminal scrolling.

---
 client/src/terminal.cpp     | 42 +++++++++++++++++++++++++++++++------
 client/src/terminal.h       |  2 ++
 client/src/ui/ui_window.cpp | 11 ++++++++++
 client/src/ui/ui_window.h   |  1 +
 4 files changed, 50 insertions(+), 6 deletions(-)

diff --git a/client/src/terminal.cpp b/client/src/terminal.cpp
index 58ce1f1..b620bdb 100644
--- a/client/src/terminal.cpp
+++ b/client/src/terminal.cpp
@@ -1,6 +1,7 @@
 #include <cstdio>
 #include <SDL3/SDL.h>
 #include <GL/glew.h>
+#include <SDL3/SDL_events.h>
 
 #include "gfx/txt_renderer.h"
 #include "terminal.h"
@@ -8,6 +9,7 @@
 Terminal::Terminal(void) {
   /* Placeholder welcome message to history. */
   _history.push_back("Welcome to Bettola");
+  _scroll_offset = 0;
 }
 
 void Terminal::_on_ret_press(void) {
@@ -26,6 +28,15 @@ void Terminal::_on_ret_press(void) {
   }
 
   _input_buffer.clear();
+  /* TODO: Ugly hack. Refactor to pass window height
+   * We need the window height to know if we should
+   * auto-scroll, but we don't have it here.
+   * Assume the height of 500 for now.
+   */
+  int visible_lines = (500-5.0f)/20.0f; /* Subtract padding. */
+  if((int)_history.size()+1 > visible_lines) {
+    _scroll_offset = (_history.size()+1) - visible_lines+1;
+  }
 }
 
 void Terminal::handle_input(SDL_Event* event) {
@@ -42,8 +53,27 @@ void Terminal::handle_input(SDL_Event* event) {
   }
 }
 
+void Terminal::scroll(int amount, int win_content_height) {
+  /* amount > 0 = scroll up. amount < 0 = scroll down. */
+  _scroll_offset += amount;
+
+  /* Lower bound: Don't scroll below the top of the history. */
+  if(_scroll_offset < 0) {
+    _scroll_offset = 0;
+  }
+  /* Upper bound: Don't scroll past the last command. */
+  float line_height = 20.0f;
+  int visible_lines = win_content_height / line_height;
+  int max_scroll = (_history.size()+1) - visible_lines;
+  if(max_scroll < 0) max_scroll = 0;
+  if(_scroll_offset > max_scroll) {
+    _scroll_offset = max_scroll;
+  }
+}
+
 void Terminal::render(TextRenderer* renderer, int x, int y, int width, int height,
                       bool show_cursor) {
+
   float white[]     = { 1.0f, 1.0f, 1.0f };
   float green[]     = { 0.2f, 1.0f, 0.2f };
   float line_height = 20.0f;
@@ -53,19 +83,19 @@ void Terminal::render(TextRenderer* renderer, int x, int y, int width, int heigh
   glEnable(GL_SCISSOR_TEST);
   glScissor(x, y, width, height);
 
-  /* Draw history. */
-  for(size_t i = 0; i < _history.size(); ++i) {
-    float y_pos = (y+height) - padding - line_height - (i*line_height);
+  /* Draw History. */
+  for(size_t i = _scroll_offset; i < _history.size(); ++i) {
+    float y_pos = (y+height) - padding - line_height - ((i - _scroll_offset) * line_height);
     renderer->render_text(_history[i].c_str(), x+padding, y_pos, 1.0f, white);
   }
 
   /* Draw current input line. */
-  std::string prompt = "> ";
-  std::string line_to_render = prompt + _input_buffer;
+  std::string line_to_render = "> " + _input_buffer;
   if(show_cursor) {
     line_to_render += "_";
   }
-  float prompt_y_pos = (y+height) - padding - line_height - (_history.size()*line_height);
+  float prompt_y_pos = (y+height) - padding - line_height
+    - ((_history.size()-_scroll_offset)*line_height);
   renderer->render_text(line_to_render.c_str(), x+padding, prompt_y_pos, 1.0f, green);
 
   /* Disable scissor test. */
diff --git a/client/src/terminal.h b/client/src/terminal.h
index 7c1049b..b68c483 100644
--- a/client/src/terminal.h
+++ b/client/src/terminal.h
@@ -11,10 +11,12 @@ public:
 
   void handle_input(SDL_Event* event);
   void render(TextRenderer* renderer, int x, int y, int width, int height, bool show_cursor);
+  void scroll(int amount, int content_height);
 
 private:
   void _on_ret_press(void);
 
   std::string _input_buffer;
   std::vector<std::string> _history;
+  int _scroll_offset;
 };
diff --git a/client/src/ui/ui_window.cpp b/client/src/ui/ui_window.cpp
index 294ac88..4ee6dce 100644
--- a/client/src/ui/ui_window.cpp
+++ b/client/src/ui/ui_window.cpp
@@ -11,6 +11,7 @@ UIWindow::UIWindow(const char* title, int x, int y, int width, int height) {
   _height       = height;
   _content      = nullptr;
   _is_dragging  = false;
+  _is_hovered   = false;
   _is_focused   = false; /* Not focused by default? */
 }
 
@@ -88,6 +89,16 @@ void UIWindow::handle_event(SDL_Event* event) {
       _x = event->motion.x - _drag_offset_x;
       _y = event->motion.y - _drag_offset_y;
     }
+
+    /* Check if mouse hovered over window. */
+    _is_hovered = is_point_inside(event->motion.x, event->motion.y);
+  } else if(event->type == SDL_EVENT_MOUSE_WHEEL) {
+    /* Only scroll window if mouse is hovering. */
+    if(_is_hovered && _content) {
+      /* SDL's wheel motion is negative scroll up on the y. */
+      int content_height_gl = _height - title_bar_height;
+      _content->scroll(-event->wheel.y, content_height_gl);
+    }
   }
 }
 
diff --git a/client/src/ui/ui_window.h b/client/src/ui/ui_window.h
index b10a7d1..029b7f3 100644
--- a/client/src/ui/ui_window.h
+++ b/client/src/ui/ui_window.h
@@ -23,6 +23,7 @@ private:
   std::string _title;
   Terminal* _content;
   bool _is_focused; /* Managed by desktop. */
+  bool _is_hovered; /* Send scroll events even if not focused. */
 
   bool _is_dragging;
   int _drag_offset_x, _drag_offset_y;