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Category: Learning

Tutorial: Saving WebCanvas Images to Disk

The WebCanvas control is used for drawing graphics in web apps. It takes advantage of the HTML5 Canvas making it fast and powerful. Sometimes is can be useful to be able to save the graphics drawn in the WebCanvas to an image file, but unfortunately there is no built-in Xojo method to do this.

However, by using a little JavaScript you can easily add this capability to Xojo.

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Web Services: Xojo Web, at your service

Using Xojo Web to create complete web apps and solutions means not having to learn a bunch of interpreted languages and dozens of ever-changing frameworks. I’m looking at you: HTML, CSS (is that even a language?), JavaScript, PHP, et al. Of course, Xojo Web not only makes it possible to create your own web apps, but it also acts as the perfect middleware that your desktop and iOS apps can communicate with. Learn about APIs and web services with Xojo in the tutorial blog post.

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Tutorial: Active Words

Follow this tutorial to learn how to create active (clickable) words in a text of a TextArea control using the OOP Delegate design pattern, which allows you to dynamically change how your app will react when the user clicks on any of these active words. Best of all, this is cross-platform, so you can use it for macOS, Windows and Linux deployments!

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#JustCode Challenge Week 1 – Color Picker

It’s the first week of the Just Code challenge so I’m starting with something pretty simple. This app lets you choose a color using the system color picker and then shows you the color values in hexadecimal (useful for programming, HTML and CSS), RGB (red, green, blue), HSV (hue, saturation,value) and CMY (cyan, magenta, yellow).

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Create a Preferences Class with Operator_Lookup

Xojo is an Object Oriented Programming Language and, among other things, that means that it supports Methods Overloading. We have seen in other posts that some of these overloaded methods can be Class Constructors, but, there are others things you can do. For example, we can overload the operators. These are the methods in charge of adding two instances of the same class, subtracting, multiplying or dividing them. But we also have at our disposal another operator we can overload: Lookup. What advantages does this give us and how it does it work? Let’s explore it while building a Preferences class we can use in any of our projects.

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Prepare Your Classes to Work in Simulated or Real Modes

In many of our development projects, if not all, we are confronted with situations when we need to test our classes before the final deployment of a project. I’m not talking about Unit Testing here, though I highly recommend the excellent session on that topic from XDC 2018.

For example, it would not be desirable to send hundreds of emails to all the entries in a database simply to test one of the workflow steps or to verify that emails are being delivered as expected. It would be a lot simpler, and less disruptive to those using your app, to test using a few email addresses that are under your control.

So let’s establish a mechanism that allows us tell our apps when to run in a “simulated” mode vs. a “real” mode for all or some of the components that we need to test along the development cycle.

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Create Your Own ImageWell Based on Canvas

Whether you are using Xojo to create your very first application or if you are coming from other languages, like C# or VisualBasic, customized UI controls are probably one of those things you have in your to-do list. For multiplatform Desktop apps, you will find that the Canvas class offers everything you need. In order to show you how easy it can be, follow this tutorial to recreate the ImageWell UI class control, provided by default in the Xojo framework. Our customized ImageWell will be able to proportionally display any JPEG file dropped by the user on the control, centering it on the available surface.

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Compilers 109 – Linking and Wrap-up

The linker is not technically part of the compiler, but it is needed to make a completed app. The purpose of the linker is to combine (link) all the various bits and pieces of machine code created by the compiler along with the necessary information to create a runnable app for the OS.

This is the ninth and final post in our Compiler series. Previous posts:

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Compilers 108 – Code Generation

Code generation is one of the last steps of the compiler. This is where the compiler emits actual machine code for the IR that was previously created.

This is the eighth post in our Compiler series. Other posts:

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Casting, get ready and keep the Type!

Object Oriented Programming (OOP) puts in our hands the ability to create apps in a flexible and powerful way. Xojo embraces that philosophy in the Xojo language itself, allowing us to implement code in a flexible way for reuse, extension and maintainability that reduces the development cycles. One of these language tools is, in fact, common in other low level programming languages: Casting or type conversion. If you are interested in this (and you should be), continue reading and discover what it is, why you should be interested in it and how can you use it in your next Xojo app!

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