Delphi basics as a downloadable windows program

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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.

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. 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. Dialog windows you use to display critical information to the user are, in most cases, displayed modally. Your custom dialogs are displayed using the ShowModal method of a form. To 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.

Mac OS Apple. Linux - Unix - 2. Linux - Unix 3 - 4. MS - DOS. Windows - 2 - 3 New. Programming languages. Assembly - 2. Cobol - 2. Cobol 3 - 4. Delphi - 2. Pascal - 2. Visual Basic - 2. Visual Basic NET - 2. It talks about thread synchronization and the mechanisms used to obtain this synchronization, including TMonitor, thread-safe queues, and TEvent.

By the end of this chapter, you will be able to create and communicate with background threads, leaving the main thread free to update your GUI or communicate with the OS. Chapter 5, Putting Delphi on the Server, focuses on how well Delphi can behave when running on a server.

Some people think that Delphi is a client-only tool, but it is not true; the number of Delphi server-side systems running all over the world prove it!

In this chapter, we'll show how to create powerful servers that offer services over a network. Then, in one of the recipes, we'll also implement a JavaScript client that brings the database data to the user's browser. The techniques explained in this chapter open a range of possibilities, especially in the mobile and web area.

If you are interested in mobile development, I think that this will be your favorite chapter! Mobiles are everywhere and this chapter will explain how to write software for your Android or iOS device, what are the best practices to use, how to save your data on your mobile device, how to retrieve and update remote data, and how to integrate with a mobile operating system.

Chapter 7, Using Specific Platform Features, shows you how to integrate your app with the underlying mobile operating systems beyond what FireMonkey offers. These are ready-to-use recipes that will be useful every day and have been selected ahead of a lot of others because although they may be obvious for some experienced users, they are still very useful. Even if there is no specically database-related code, many of the recipes can also be used or sometimes especially used when you are dealing with data.

They have been introduced in Delphi XE2 and are still one of the less-known features for the good old Delphi developers. However, as usual, some businessmen say looks matter, so the look and feel of your application could be one of the reasons to choose your product over one from a competitor.

Consider that with a few mouse clicks you can apply many different styles to your application to change the look and feel of your applications. So why not give it a try? VCL styles are a completely different beast to FireMonkey styles. They are both styles but with completely different approaches and behavior. To get started with VCL styles, we'll use a new application. The following screenshot is the resultant form that runs on a Windows 7 machine: A form without style How to do it Now we've to apply a set of nice styles.

To do this, perform the following steps: 1. Navigate to Project Options. In the resultant dialog, go to Application Appearance and select all the styles that we want to include in our application. Using the Preview button, the IDE shows a simple demo form with some controls, and we can get an idea about the nal result of our styled form. Feel free to experiment and choose the styleor set of stylesthat you like. Only one style will be used at a time, but we can link the necessary resources to the executable and select the proper one at runtime.

After selecting all the required styles from the list, we've to select one in the combobox at the bottom of the screen. This style will be the default style for our form and will be loaded as soon as the application starts. You can delay this choice and make it at runtime using code if you prefer.

The resultant form is shown in the following screenshot: The same form as the preceding one but with the Iceberg Classico style applied How it works Selecting one or more styles by navigating to Project Options Application Appearance can cause the Delphi linker to link the style resource to your executable. It is possible to link many styles to your executable, but you can use only one style at time.

So, how does Delphi know which style you want to use when there are more than one styles? If we check the Project le the le with the. The following lines are the interesting part: begin Application. Initialize; Application. Run; end. TrySetStyle static method. We'll see more about it in the next recipe when we'll learn how to change a style at runtime. There's more Moreover, it is possible to create your own styles or modify the existing ones by using the Bitmap Style Designer available at Tools Bitmap Style Designer menu.

One of the main features of a VCL style is the ability to change the style while an application is running. Getting ready Because a VCL style is simply a particular kind of binary le, we can allow our users to load their preferred style at runtime, and we can even provide new stylespublishing them on a website or sending them by an e-mail to our customers. In this recipe, we'll be able to change the style while an application is running using a style already linked at design time or let the user choose between a set of styles deployed inside a folder.

Create a brand new VCL application and add the Vcl. Themes and Vcl. Styles units to the main implementation form. These units are required to use VCL styles at runtime.

Leave the default component names. Go to Project Appearance and select eight styles of your choice from the list. Leave the Default style option to Windows. The TStyleManager. StyleNames property contains all names of the available styles. In the FormCreate event handler, we have to load the already linked styles present in the executable to the listbox to let the user choose one of them. StylesListRefresh; var stylename: string; begin ListBox1.

StyleNames do begin ListBox1. Add stylename ; end; end; 5. In the Button1Click event handler, we've to set the current style according to the one selected from ListBox1 using the following code: TStyleManager. SetStyle ListBox1. ItemIndex] ; 6. The Button2Click event handler should allow the user to select a style from disk. So, we have to create a folder named styles at level of our executable and copy a few. After copying the les, write the following code under the Button2Click event handler.

This code allows the user to chose a style le directly from the disk. Then you can select one of the loaded styles from the listbox and click on Button1 to apply it to the application. The code is as follows: if OpenDialog1. Execute then begin if TStyleManager. IsValidStyle OpenDialog1. FileName then For More Information: www.

LoadFromFile OpenDialog1. Just to have an idea of how the different controls appear with the selected style, drag- and-drop some controls to the right-hand side of the form. The following screenshot shows an application with some styles loaded, some at design time and some from the disk. Hit F9 or go to Run Run and play with your application using and loading styles from the disk. LoadFromFile 'StylePathFi leName' After loading new styles from the disk, these new styles are completely similar to the styles linked to the executable during the compile and link phases and can be used in the same way.

Other things to consider are third-party controls. If your application uses third-party controls, take care with their style support. If your external components do not support styles, you will end up with some controls styled the original included in Delphi and some not your external third-party controls!

Sometimes, even a simple concept is easier to understand and nicer to see if it is represented by images. In this recipe, we'll see how to customize the TDBGrid object to visualize graphical representation of data. This means that we can use simple event handlers to draw standard components in different ways. It is not always simple, but TDBGrid is customizable in a really easy way.

Let's say that we have a class of musicians that have to pass a set of exams. We want to show the percentage of musicians who have already passed exams with a progress bar, and if the percent is higher than 50 percent, there should also be a check in another column.

If some of the code seems unclear at the moment, consider the in-memory table as a normal TDataSet descendant. To customize TDBGrid, perform the following steps: 1. Set the TDBGrid font size to This will create more space in the cell for our graphical representation.

In a real application, we should load real data from some sort of database. But for now, we'll use some custom data generated in code. We have to load this data into the dataset with the following code: procedure TMainForm. InsertRecord For More Information: www. InsertRecord ['Giuseppe Verdi',30,5] ; end; 4. Do you remember? We've two calculated elds that need to be lled in some way. FieldByName 'PassedExams'.

FieldByName 'TotalExams'. Run the application by hitting F9 or navigating to Run Run and you will get the following screenshot: A normal form with some data 6. This is useful, but a bit boring. Let's start our customization. Close the application and return to Delphi IDE. All the customization code goes in this event. Include the Vcl. Style; end; if Column. Width; Grid.

Size - 1; Grid. RoundRect R. Left, R. Top, Trunc R. Bottom, 2, 2 ; InflateRect R, -1, -1 ; Grid. TextExtent S ; Grid. TextOut R. Width div 2 - SSize. Height div 2 - SSize. Equals 'MoreThan50Percent' then begin Grid. FillRect R ; if Column. Check out the help on ShellExecute for a full description of parameters and error codes returned.

You can open any document without knowing which program is associated with it—the link is defined in the Windows Registry. Here are some shell examples. Here's how to find an application associated with an extension. Here's how to send an email with the attachment. There are flexible software development tools. With this utility , users are able to import and examine various datasets. In addition, it is possible to utilize word frequency tables and intelligent query options.

This utility helps you design complex integrated circuits. There are instruments for simulating the voltage and analyzing behavior of every component. This program is oriented toward software developers.

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