Click-and-Drag Selection

1#include <SDL.h>
2#include <iostream>
3#include "Window.h"
4
5class SelectionBox {
6 public:
7  void Tick() {
8    int MouseX, MouseY;
9    Uint32 Buttons = SDL_GetMouseState(
10      &MouseX, &MouseY);
11
12    if (Buttons & SDL_BUTTON_LMASK) {
13      if (!IsSelecting) {
14        // Start new selection
15        StartX = MouseX;
16        StartY = MouseY;
17        IsSelecting = true;
18      }
19
20      // Calculate rectangle bounds
21      CurrentX = MouseX;
22      CurrentY = MouseY;
23
24      int Left = std::min(StartX, CurrentX);
25      int Right = std::max(StartX, CurrentX);
26      int Top = std::min(StartY, CurrentY);
27      int Bottom = std::max(StartY, CurrentY);
28
29      int Width = Right - Left;
30      int Height = Bottom - Top;
31
32      std::cout << "Selection: Position("
33        << Left << ", " << Top << ") "
34        << "Size(" << Width << ", "
35        << Height << ")\n";
36    } else if (IsSelecting) {
37      // Selection complete
38      IsSelecting = false;
39      PrintFinalSelection();
40    }
41  }
42
43 private:
44  bool IsSelecting{false};
45  int StartX{0}, StartY{0};
46  int CurrentX{0}, CurrentY{0};
47
48  void PrintFinalSelection() {
49    int Left = std::min(StartX, CurrentX);
50    int Right = std::max(StartX, CurrentX);
51    int Top = std::min(StartY, CurrentY);
52    int Bottom = std::max(StartY, CurrentY);
53
54    std::cout << "Final selection area: ("
55      << Left << ", " << Top << ") to ("
56      << Right << ", " << Bottom << ")\n";
57  }
58};
59
60int main(int argc, char** argv) {
61  SDL_Init(SDL_INIT_VIDEO);
62  Window GameWindow;
63  SelectionBox Selection;
64  SDL_Event E;
65
66  while (true) {
67    while (SDL_PollEvent(&E)) {
68      // Handle other events...
69    }
70
71    Selection.Tick();
72    GameWindow.Update();
73  }
74
75  SDL_Quit();
76  return 0;
77}

1#include <SDL.h>
2
3class AdvancedSelectionBox {
4 public:
5  void Tick() {
6    int MouseX, MouseY;
7    Uint32 Buttons = SDL_GetMouseState(
8      &MouseX, &MouseY);
9
10    if (Buttons & SDL_BUTTON_LMASK) {
11      if (!IsSelecting) {
12        StartX = MouseX;
13        StartY = MouseY;
14        IsSelecting = true;
15      }
16
17      CurrentX = MouseX;
18      CurrentY = MouseY;
19
20      // Add minimum size requirement
21      int Width = std::abs(CurrentX - StartX);
22      int Height = std::abs(CurrentY - StartY);
23
24      if (Width < MinimumSize) {
25        CurrentX = StartX + (CurrentX > StartX
26          ? MinimumSize : -MinimumSize);
27      }
28
29      if (Height < MinimumSize) {
30        CurrentY = StartY + (CurrentY > StartY
31          ? MinimumSize : -MinimumSize);
32      }
33
34      // Snap to grid
35      CurrentX = (CurrentX / GridSize) * GridSize;
36      CurrentY = (CurrentY / GridSize) * GridSize;
37
38      PrintSelection();
39    } else if (IsSelecting) {
40      IsSelecting = false;
41      PrintFinalSelection();
42    }
43  }
44
45 private:
46  static const int MinimumSize = 10;
47  static const int GridSize = 8;
48  bool IsSelecting{false};
49  int StartX{0}, StartY{0};
50  int CurrentX{0}, CurrentY{0};
51};