SDL2 resize window

[Pe3s]

Hello forum members, how can I get rid of the window copy effect when resizing (empty window) without an open image?

Code: Pascal  [Select][+][-]

1. unit Unit1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, Forms, Controls, Graphics, Dialogs, ComCtrls, ExtCtrls,
9.   StdCtrls, SDL2, SDL2_image, Math;
10.  
11. type
12.  
13.   { TForm1 }
14.  
15.   TForm1 = class(TForm)
16.     Button1: TButton;
17.     Button2: TButton;
18.     Button3: TButton;
19.     Button4: TButton;
20.     OpenDialog1: TOpenDialog;
21.     Panel1: TPanel;
22.     Panel2: TPanel;
23.     StatusBar1: TStatusBar;
24.     procedure Button1Click(Sender: TObject);
25.     procedure FormDestroy(Sender: TObject);
26.     procedure FormResize(Sender: TObject);
27.     procedure FormShow(Sender: TObject);
28.   private
29.       SDLWindow: PSDL_Window;
30.       SDLRenderer: PSDL_Renderer;
31.       CurrentTexture: PSDL_Texture;
32.       procedure InitializeSDL;
33.       procedure ShutdownSDL;
34.       procedure LoadAndDisplayImage(const FileName: string);
35.       procedure RenderImage;
36.  
37.   public
38.  
39.   end;
40.  
41. var
42.   Form1: TForm1;
43.  
44. implementation
45.  
46. {$R *.lfm}
47.  
48. { TForm1 }
49.  
50. procedure TForm1.Button1Click(Sender: TObject);
51. begin
52.   if OpenDialog1.Execute then
53.     LoadAndDisplayImage(OpenDialog1.FileName);
54. end;
55.  
56. procedure TForm1.FormDestroy(Sender: TObject);
57. begin
58.   ShutdownSDL;
59. end;
60.  
61. procedure TForm1.FormResize(Sender: TObject);
62. begin
63.   RenderImage;
64. end;
65.  
66. procedure TForm1.FormShow(Sender: TObject);
67. begin
68.    InitializeSDL;
69. end;
70.  
71. procedure TForm1.InitializeSDL;
72. begin
73.   if SDL_Init(SDL_INIT_VIDEO) < 0 then
74.     raise Exception.Create('Could not initialize SDL: ' + SDL_GetError);
75.  
76.   SDLWindow := SDL_CreateWindowFrom(Pointer(Panel1.Handle));
77.   if SDLWindow = nil then
78.     raise Exception.Create('Could not create SDL window: ' + SDL_GetError);
79.  
80.   SDLRenderer := SDL_CreateRenderer(SDLWindow, -1, SDL_RENDERER_ACCELERATED);
81.   if SDLRenderer = nil then
82.     raise Exception.Create('Could not create SDL renderer: ' + SDL_GetError);
83.  
84.   if IMG_Init(IMG_INIT_PNG or IMG_INIT_JPG) = 0 then
85.     raise Exception.Create('Could not initialize SDL_image: ' + IMG_GetError);
86. end;
87.  
88. procedure TForm1.ShutdownSDL;
89. begin
90.    if CurrentTexture <> nil then
91.     SDL_DestroyTexture(CurrentTexture);
92.   if SDLRenderer <> nil then
93.     SDL_DestroyRenderer(SDLRenderer);
94.   if SDLWindow <> nil then
95.     SDL_DestroyWindow(SDLWindow);
96.   IMG_Quit;
97.   SDL_Quit;
98. end;
99.  
100. procedure TForm1.LoadAndDisplayImage(const FileName: string);
101. begin
102.    // Clean up the old texture if it exists
103.   if CurrentTexture <> nil then
104.     SDL_DestroyTexture(CurrentTexture);
105.  
106.   // Load the new image as a texture
107.   CurrentTexture := IMG_LoadTexture(SDLRenderer, PChar(FileName));
108.   if CurrentTexture = nil then
109.     raise Exception.Create('Could not load texture: ' + IMG_GetError);
110.  
111.   // Render the image to fit the new size
112.   RenderImage;
113. end;
114.  
115. procedure TForm1.RenderImage;
116. var
117.   SrcRect, DstRect: TSDL_Rect;
118.   ImgWidth, ImgHeight: Integer;
119.   PanelWidth, PanelHeight: Integer;
120.   AspectRatio: Double;
121. begin
122.   if CurrentTexture = nil then
123.     Exit;
124.  
125.   // Get image dimensions
126.   SDL_QueryTexture(CurrentTexture, nil, nil, @ImgWidth, @ImgHeight);
127.  
128.   // Get panel dimensions
129.   PanelWidth := Panel1.Width;
130.   PanelHeight := Panel1.Height;
131.  
132.   // Calculate aspect ratio to fit the image proportionally
133.   AspectRatio := Min(PanelWidth / ImgWidth, PanelHeight / ImgHeight);
134.  
135.   DstRect.w := Round(ImgWidth * AspectRatio);
136.   DstRect.h := Round(ImgHeight * AspectRatio);
137.   DstRect.x := (PanelWidth - DstRect.w) div 2;
138.   DstRect.y := (PanelHeight - DstRect.h) div 2;
139.  
140.   // Render the image
141.   SDL_RenderClear(SDLRenderer);
142.   SDL_RenderCopy(SDLRenderer, CurrentTexture, nil, @DstRect);
143.   SDL_RenderPresent(SDLRenderer);
144.  
145. end;
146.  
147. end.
148.  
149.