src/tests/servers/app/draw_after_children/DrawAfterChildren.cpp

   1
   2 #include <stdio.h>
   3
   4 #include <Application.h>
   5 #include <View.h>
   6 #include <Window.h>
   7
   8 /*-----------------------------------------------------------------------------
   9
  10 OBSERVATION on R5 behaviour:
  11
  12 * The hook function DrawAfterChildren is not called at all if the
  13   view flags don't include B_DRAW_ON_CHILDREN.
  14
  15 * If the view flags include B_DRAW_ON_CHILDREN, then any drawing commands
  16   executed in Draw() AND DrawAfterChildren() will paint on top of children.
  17
  18 * The background of a view with the B_DRAW_ON_CHILDREN flag set will not
  19   be painted by the app_server when child views change position and areas
  20   in the parent view are "exposed". If the expose events have other reasons,
  21   the background is painted as usual.
  22
  23 * The app_server side background painting of child views does not occur
  24   after the Draw() hook of the parent view with B_DRAW_ON_CHILDREN has been
  25   called. So while DrawAfterChildren() may be called after the Draw() hooks
  26   of all children have been called, the background has been painted earlier.
  27
  28 * It looks like the background painting inside app_server of a view with
  29   B_DRAW_ON_CHILDREN paints over the background of any children, though
  30   the background of the children is later painted too. Therefor, if a child
  31   has B_TRANSPARENT_COLOR background, the background of the parent with
  32   B_DRAW_ON_CHILDREN stays visible in the area of that child.
  33
  34 * Both Draw() and DrawAfterChildren() appear to push their own graphics
  35   states onto the state stack.
  36
  37
  38 CONCLUSION:
  39
  40 It looks like the B_DRAW_ON_CHILDREN flag causes two effects:
  41
  42 * The local view clipping region inside the app_server simply ignores
  43   any children, this effects any drawing commands, those from Draw()
  44   and those from DrawAfterChildren()
  45
  46 * The DrawAfterChildren() hook is called after the children have drawn,
  47   so that the user may move all drawing functions there which he does not
  48   wish to have painted over by children.
  49
  50 That areas exposed by moving child views are not repainted could
  51 be considered a bug of the R5 implementation.
  52
  53 -----------------------------------------------------------------------------*/
  54
  55
  56
  57 class TestView : public BView {
  58 public:
  59         TestView(BRect frame);
  60         ~TestView();
  61
  62         virtual void Draw(BRect updateRect);
  63         virtual void DrawAfterChildren(BRect updateRect);
  64 };
  65
  66
  67 TestView::TestView(BRect frame)
  68         : BView(frame, "TestView", B_FOLLOW_ALL,
  69                 B_WILL_DRAW | B_DRAW_ON_CHILDREN | B_FULL_UPDATE_ON_RESIZE)
  70 {
  71         SetViewColor(200, 220, 255);
  72 }
  73
  74
  75 TestView::~TestView()
  76 {
  77 }
  78
  79
  80 void
  81 TestView::Draw(BRect updateRect)
  82 {
  83         printf("Draw(BRect(%.1f, %.1f, %.1f, %.1f))\n",
  84                 updateRect.left, updateRect.top, updateRect.right, updateRect.bottom);
  85
  86         printf("pensize: %.2f\n", PenSize());
  87
  88         SetHighColor(0, 0, 255);
  89         StrokeLine(Bounds().LeftBottom(), Bounds().RightTop());
  90
  91         SetPenSize(5);
  92 }
  93
  94 void
  95 TestView::DrawAfterChildren(BRect updateRect)
  96 {
  97         printf("DrawAfterChildren(BRect(%.1f, %.1f, %.1f, %.1f))\n",
  98                 updateRect.left, updateRect.top, updateRect.right, updateRect.bottom);
  99
 100         printf("pensize: %.2f\n", PenSize());
 101
 102         SetHighColor(255, 0, 0);
 103         StrokeLine(Bounds().LeftTop(), Bounds().RightBottom());
 104         Sync();
 105
 106         SetPenSize(7);
 107 }
 108
 109
 110 //      #pragma mark -
 111
 112 class ChildView : public BView {
 113 public:
 114         ChildView(BRect frame, const char* name, rgb_color viewColor);
 115         ~ChildView();
 116
 117         virtual void Draw(BRect updateRect);
 118 };
 119
 120
 121 ChildView::ChildView(BRect frame, const char* name, rgb_color viewColor)
 122         : BView(frame, name, B_FOLLOW_ALL, 0)
 123 {
 124         SetLowColor(200, 200, 200);
 125         SetViewColor(viewColor);
 126         if (*(int32*)&viewColor == *(int32*)&B_TRANSPARENT_COLOR)
 127                 SetFlags(Flags() | B_WILL_DRAW);
 128 }
 129
 130
 131 ChildView::~ChildView()
 132 {
 133 }
 134
 135
 136 void
 137 ChildView::Draw(BRect updateRect)
 138 {
 139         FillRect(updateRect, B_SOLID_LOW);
 140 }
 141
 142
 143 // #pragma mark -
 144
 145
 146 int
 147 main(int argc, char** argv)
 148 {
 149         BApplication app("application/x-vnd.Haiku-DrawAfterChildren");
 150
 151         BRect frame(100, 100, 700, 400);
 152         BWindow* window = new BWindow(frame, "Window",
 153                 B_TITLED_WINDOW, B_QUIT_ON_WINDOW_CLOSE);
 154
 155         frame.OffsetTo(B_ORIGIN);
 156         TestView* view = new TestView(frame);
 157         window->AddChild(view);
 158
 159         frame.InsetBy(20, 20);
 160         frame.right = frame.left + frame.Width() / 2 - 10;
 161         BView* child = new ChildView(frame, "child 1",
 162                 (rgb_color){ 200, 200, 200, 255 });
 163         view->AddChild(child);
 164
 165         frame.OffsetBy(frame.Width() + 20, 0);
 166         child = new ChildView(frame, "child 2", B_TRANSPARENT_COLOR);
 167         view->AddChild(child);
 168
 169         window->Show();
 170
 171         app.Run();
 172         return 0;
 173 }
 174