Žarko Gajić | On Delphi Programming

Time 2020-10-09 22:04:36

Web Name: Žarko Gajić | On Delphi Programming

WebSite: http://zarko-gajic.iz.hr

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Windows messages are a key ingredient in communication between Windows and (your) application and also in communication between (two) applications.Even without your knowledge Windows messages are being posted and handled by forms in your application. For example, when the user closes the form in your application, the WM_CLOSE message is sent to the window/form and the form gets closed (if you do not react programmatically).For an application to receive a Window message, the application must provide a *window* a message will be sent to. In normal situation this window is the (main) form in your application. You write a procedure to handle a specific message, like WM_NCHitTest, and you are done.BUT, what if you do NOT have a window to receive a message? What if you want to handle messages in your custom class derived from TObject? Continue reading In Delphi, the reserved word interface has two distinct meanings. In a Delphi unit, “interface” denotes the start of a unit section used to declare public constants, data types, variables, procedures and functions visible and accessible to other units using this unit. In OOP jargon, an “object interface” or simply “interface” is a kind of a class with no implementation (but not like a class with abstract methods). An interface defines methods that can be implemented by a class (a class “implements” the interface). Object interfaces might be used when multiple inheritance is needed, and are frequently used when working with COM objects. For some intro to interfaces: Interfaces in Delphi Programming 101. Continue reading Delphi s TComboBox combines an edit box with a scrollable list – with the Style property defining the display style of the combo. When set to csDropDownList there’s no edit box – users can only pick from the predefined items displayed by the list. If you need to react, when the selection changes, you will write code for the OnSelect event.Now, presume our combo is a kind of a filter selector – when the selection changes you need to update some other UI control. For example, combo lists invoices and selecting one (item from its list) displays the selected invoice items in some grid control. Depending on the number of invoice items, where they are stored, how you fetch them, and so on – the actual code to (fetch items and) refresh the UI might take longer time – whatever longer means. If you scroll quickly through the combo items – OnSelect will get fired for each visited item in the list and your application might appear irresponsible, lagging and slow. Continue reading One of the common problems we programmers face (and hopefully we are aware of) are memory leaks, or leaks of any other kind of resources. For example, Windows limit the number of GDI or USER32 objects that a process can allocate at one time. When things go down the wrong road you would want to have the tools to help you find (again) the correct path to free-what-you-create. Continue reading Dialog windows you use to display critical information to the user are, in most cases, displayed modally. A modal window (form) is the one where the application can t continue to run until the modal window is closed. Delphi s ShowMessage, InputBox and MessageDlg, for example, display a modal form to the user waiting for some action. Your custom dialogs are displayed using the ShowModal method of a form.Dimmer a device for varying the brightness of lightTo emphasize the importance of a modal form and the information it presents, you could gray out the main form of the application when the modal form is activated. Continue reading “If you want it to be playable and more interesting you need to jazz it up a bit!”That’s what’s been cooking in my head from the time I’ve finished implementing the back end for the game of Memory (Match Up, Concentration, or whatever you are used to call it). As a proof of concept, I’ve coded a very simple application, aka the front end for the game – juts to have a workable user interface.Now, the time has come to finish the series and introduce a more eye candy version of the game, one that’s not using dull buttons with numbers for field display values but that actually looks like card game type of Memory, with nice fancy images/icons for game fields. Why stop there? Why not go a step forward and introduce a new dimension for the game: make it 3D having fields appear on planes/layers, so players need to switch between planes to match a pair. Continue reading I guess you know you can run your browser in full screen mode using the F11 shortcut key. Windows Explorer also supports this feature.Running in full screen, where an application UI covers the entire screen, over the TaskBar and any Desktop/Tool bars, is handy when a user has a limited screen size (laptops) or when you just want more to be visible by the browser or the Windows Explorer.Running your application in full screen might also be handy if your users want to be focused only on your application s window. Continue reading The TListView Delphi control displays a list of items in a fashion similar to how Windows File Explorer displays files and folders.The ReadOnly property of a List View, determines whether the user can modify the caption of an item. When ReadOnly is false, the OnEditing and OnEdited events occur when the user begins and finishes editing the list item, respectively.At run time the user can click the selected item to enter the edit mode. Actually, two clicks (not double click) are needed: a click on an item to select it and then a second click to go to edit mode. Here’s how to initiate the edit mode by a keyboards shortcut and also how to limit the number of characters for the TListView s editor control. Continue reading In my previous post, Coding a Game of Memory in Delphi – OOP Model, I’ve been developing the model, aka the back end, for the Memory (Match Up, Concentration, …) game. The idea was to separate the game logic from the user interface (aka the front end). As a result a few classes were introduced: TPlayer, TField and, of course, the main class/object TMemoryGame implementing all the code required to run the game. Having only the model does not help us much if we actually want to play the game. Therefore, this time, we go into building the user interface in Delphi.Since the TMemoryGame class is framework agnostic (and not platform specific), it is up for you to decide if you would like to do a classic Windows VCL application, a FireMonkey Android mobile game or something that works on a Mac. To make it quick and simple, I’ll go old-style VCL school. Continue reading Memory, Match Up, Concentration … there are many names for a simple card game I’m certain you’ve been playing with your friends at some point during your childhood. I’m also certain you are still playing it from time to time (at least I do with my kids). Just a few months ago, I’ve tried my “luck” against a robot in CosmoCaixa, Barcelona (image).The rules of the game are simple: cards are laid face down on a surface and two, per turn, are flipped face up. If the flipped cards are a match pair (same looking, same rank, save value) the player claims (wins) the pair and plays again. If they are not a match, cards are flipped face down again, and the next player takes turn. The game ends when all the pairs have been claimed and the player with the most claimed pairs is the winner. If all players have the same number of claimed pairs we can agree to have a tie, or to have the last player be the winner.I’ve always been a fan of such simple games – from my point of view they are a perfect pick if you want to start learning programming – have fun and sharpen your developer skills at the same time.While there are Delphi implementations of the game you can find online – most of them have heavily mixed the visual presentation of the game (user interface) with the model (implementation of the game logic).In my version of Memory, I’d like to separate the user interface (front end) from the game logic (back end) as much as possible. I want to create a game model in OOP style – where the game logic does not interact (or as less as possible) with the front end. Continue reading BeginEnd.netAttach objects to (animated) bones, like weapon in character’s hand, by ExposeTransformsYou can now easily attach objects to (animated) bones in your models, e.g. to attach a weapon to animated character’s hand. This is performed by setting the TCastleSceneCore.ExposeTransforms property.Melbourne Meeting – October 2020Monday 19 October at 6 for 6:15pm start. ONLINE MEETING – WE WILL NOT BE MEETING IN PERSON We will meet online, instead of meeting at the Shed. The meeting will start with the Australian Delphi User GDelphi icons to distinguish various Delphi versionsWhen installing many Delphi versions, all have similar icons. So I asked this a while ago: [WayBack] I remember someone creating version specific icons for Delphi a while ago (around XE4 era I think),Celebrating 20 days the 20 year company anniversary!It s a special year for our team as we celebrate the company s 20th birthday this month. We ve come a long way over the years, so we wanted to celebrate this together with YOU! OfficialGExperts 1.3.16 Released with Support for RAD Studio 10.4 SydneyGExperts 1.3.16 is available on the download page and on Thomas Mueller’s web site.  This release contains support for Delphi 10.4 and some bugfixes and new features. If you are have upgraded to RAD S Meta Log in Entries feed Comments feed WordPress.org

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