\u041f\u0440\u043e\u0437\u0440\u0430\u0447\u043d\u044b\u0439 TListBox
\n<\/p>\n
\u041f\u0440\u043e\u0437\u0440\u0430\u0447\u043d\u044b\u0439 TListBox\n\nunit TransparentListBox;\n\n (*\n *\n * Written by Walter Irion (CIS 114254, 2455) after the THotSpot\n * sample component that Arne Sch?pers presented in the German\n * c''t magazine (issue 6\/1996, pp. 286 ff.).\n *\n * TTransparentListBox is far from being a universal solution:\n * it does not prevent Windows'' scrolling mechanism from\n * shifting the background along with scrolled listbox lines.\n * Moreover, the scroll bar remains hidden until the keyboard\n * is used to change the selection, and the scroll buttons\n * become visible only when clicked.\n *\n * To break it short: TTransparentListBox is only suitable\n * for non-scrolling lists.\n *\n * In fact it must be possible to write a listbox component\n * that handles scrolling correctly. But my essays to intercept\n * EM_LINESCROLL messages were fruitles, even though I tried\n * subclassing via WndProc.\n *\n * A solution for transparent TEdit and TMemo controls is\n * introduced in issue 9\/1996 of the c''t magazine, again\n * by Arne Sch?pers. But these are outright monsters with\n * wrapper windows to receive notification messages as well\n * as so-called pane windows that cover the actual control''s\n * client area and display its content.\n *\n * Previous issues of the c''t magazine can be ordered from:\n *\n * c''t-Kopierservice\n * Helstorfer Str. 7\n * 30625 Hannover, Germany\n *\n * They expect a crossed cheque amounting to DM 14,00\n * to be included with your order, but I don''t know about\n * international orders.\n *\n *)\n\n interface\n\n uses\n Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,\n StdCtrls;\n\n type\n TTransparentListBox = class(TListBox)\n private\n { Private declarations }\n protected\n { Protected declarations }\n procedure CreateParams(var Params: TCreateParams); override;\n procedure WMEraseBkgnd(var Msg: TWMEraseBkgnd); message WM_ERASEBKGND;\n procedure DrawItem(Index: Integer; Rect: TRect; State: TOwnerDrawState);\n override;\n public\n { Public declarations }\n constructor Create(AOwner: TComponent); override;\n procedure SetBounds(ALeft, ATop, AWidth, AHeight: Integer); override;\n published\n { Published declarations }\n property Style default lbOwnerDrawFixed;\n property Ctl3D default False;\n property BorderStyle default bsNone;\n end;\n\n procedure Register;\n\n implementation\n\n constructor TTransparentListBox.Create(AOwner: TComponent);\n begin\n inherited Create(AOwner);\n Ctl3D := False;\n BorderStyle := bsNone;\n Style := lbOwnerDrawFixed; \/\/ changing it to lbStandard results\n \/\/ in loss of transparency\nend;\n\n procedure TTransparentListBox.CreateParams(var Params: TCreateParams);\n begin\n inherited CreateParams(Params);\n Params.ExStyle := Params.ExStyle or WS_EX_TRANSPARENT;\n end;\n\n procedure TTransparentListBox.WMEraseBkgnd(var Msg: TWMEraseBkgnd);\n begin\n Msg.Result := 1; \/\/ Prevent background from getting erased\nend;\n\n procedure TTransparentListBox.SetBounds(ALeft, ATop, AWidth, AHeight: Integer);\n var\n tlbVisible: Boolean;\n begin\n tlbVisible := (Parent <> nil) and IsWindowVisible(Handle); \/\/ Check for\n visibility\n if tlbVisible then ShowWindow(Handle, SW_HIDE); \/\/ Hide-Move-Show\n strategy...inherited SetBounds(ALeft, ATop, AWidth, AHeight); \/\/ ... to prevent\n background...if tlbVisible then ShowWindow(Handle, SW_SHOW); \/\/ ... from\n getting copied\n end;\n\n procedure TTransparentListBox.DrawItem(Index: Integer; Rect: TRect;\n State: TOwnerDrawState);\n var\n FoundStyle: TBrushStyle;\n R: TRect;\n begin\n FoundStyle := Canvas.Brush.Style; \/\/ Remember the brush style\n\n R := Rect; \/\/ Adapt coordinates of drawing\n rect...MapWindowPoints(Handle, Parent.Handle, R, 2); \/\/ ... to parent''s coordinate\n system\n InvalidateRect(Parent.Handle, @R, True); \/\/ Tell parent to redraw the\n item Position\n Parent.Update; \/\/ Trigger instant redraw\n (required)\n\n if not (odSelected in State) then\n begin \/\/ If an unselected line is being\n handled\n Canvas.Brush.Style := bsClear; \/\/ use a transparent background\n end\n else\n begin \/\/ otherwise, if the line needs to be\n highlighted,\n Canvas.Brush.Style := bsSolid; \/\/ some colour to the brush is\n essential\n end;\n\n inherited DrawItem(Index, Rect, State); \/\/ Do the regular drawing and give\n component users...\n \/\/ ... a chance to provide an\n OnDrawItem handler\n\n Canvas.Brush.Style := FoundStyle; \/\/ Boy-scout rule No. 1: leave site as\n you found it\n end;\n\n procedure Register;\n begin\n RegisterComponents('Samples', [TTransparentListBox]);\n end;\n\n end.\n<\/div><\/pre>\n<\/p>\n","protected":false},"excerpt":{"rendered":"
\u041f\u0440\u043e\u0437\u0440\u0430\u0447\u043d\u044b\u0439 TListBox<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[413,386],"tags":[582,1631],"_links":{"self":[{"href":"http:\/\/pblog.ru\/lab\/index.php?rest_route=\/wp\/v2\/posts\/788"}],"collection":[{"href":"http:\/\/pblog.ru\/lab\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/pblog.ru\/lab\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/pblog.ru\/lab\/index.php?rest_route=\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"http:\/\/pblog.ru\/lab\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=788"}],"version-history":[{"count":0,"href":"http:\/\/pblog.ru\/lab\/index.php?rest_route=\/wp\/v2\/posts\/788\/revisions"}],"wp:attachment":[{"href":"http:\/\/pblog.ru\/lab\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=788"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/pblog.ru\/lab\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=788"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/pblog.ru\/lab\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=788"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}