# Stage 1

## Overview

In the first stage of the Cityscape Challenge, we will draw the shapes of buildings with different sizes. Because we will be drawing lots of buildings, we will automate the process using functions and variables.

## Draw a Building

A building is a filled in rectangle. We use context.fillStyle to set the color of the rectangle, and context.fillRect() to draw the rectangle.

In this example, we draw a building that is blue (the color #1E90FF), 160 pixels wide, 240 pixels tall, and positioned so its top left corner is at (100, 50).

In the context's coordinate system, the origin (0, 0) is at the top left corner of the canvas, and the x-coordinates increase moving to the right and the y-coordinates increase moving down. So, the rectangle is positioned 100 pixels to the right and 50 pixels down from the top left corner of the canvas.

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## Challenge 1

Draw a building (a rectangle) that is 320 pixels wide and 160 pixels tall so the bottom left corner of the building is covering the x at (40, 240) and the top right corner is covering the other x, but not covering the red x's.

Remember, the point (40, 240) is 40 pixels to the right and 240 pixels down from the origin, which is the top left corner of the canvas.

We are positioning the building's bottom left corner so the building is sitting on the ground. You will have to do some math to find the coordinates of the building's top left corner.

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## Use Variables to Size and Position a Building

We can use variables to automatically size and position a building.

In this example, we draw a green building (color #228B22) that is twice as tall as it is wide, and sitting on the ground at (60, 280).

To change the size of the building, all we do is store a different value in the variable w. The program automatically calculates the height of the building (assigning it to the variable h) and the y-coordinate of the top of the building (assigning it to the variable y). These variables are then used to draw the building.

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## Challenge 2

For our cityscape, we don't want think about buildings in terms of pixels. We want to size buildings based on the number of floors they have and the number of office units on each floor, and then write the program so it calculates the number of pixels for us.

Each office unit is 16 pixels wide and 16 pixels tall. The outer walls, roof, and floor of the building are each 4 pixels thick.

Write a program to calculate the size and position of the building for you. The variable units stores the number of office units on each floor. The variable floors stores the number of floors in the building.

Then draw a gray (color #999999) building with 10 floors and 8 office units on each floor sitting on the ground at (120, 280).

To see the office units in your building, add the line "drawOffices(x, y, w, h);" to the end of your program, where (x, y) are the coordinates of the top left corner of your building, and w and h are the width and height of your building.

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Previous Challenge: View your code from Stage 1 Challenge 1 to use on this challenge.

Code Missing: You have not yet entered any code in to the previous challenge: Stage 1 Challenge 1
Stage 1 Challenge 1
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## Use a Function to Draw a Building

Drawing a single building takes quite a few steps. We have to calculate the width and height of the building, and the y-coordinate of the top of the building. Then we have to set the building color and draw the rectangle. Once we start drawing in windows, the list of steps will get much longer.

To draw our cityscape, we have to draw dozens of buildings. Typing in all that code for each building is going to be a lot of work.

If there is a chunk of code that you are going to use over and over again, putting that code into a function can make your life much easier. Then, to run the code, all you have to do is call the function by typing one line.

In this example, we create a function that will draw a French flag. Because we might want to draw a French flag in lots of different places, we make the x- and y-coordinates of the flag variables. When we call drawFrenchFlag(30, 100), the 30 is assigned to the variable x and the 100 is assigned to the variable y inside of the function. Now we can easily draw as many French flags as we want!

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## Challenge 3

Write a function to draw the building from Challenge 2. The function will be passed four values that it will assign to the following four variables (called parameters). The first parameter, leftX, is the x-coordinate of the left side of the building. The second parameter, groundY, is the y-coordinate of the base of the building. The third parameter, units, is the number of office units on a floor. The fourth parameter, floors, is the number of floors in the building.

Then use the function to draw two buildings. The first building will have 12 floors and 8 office units per floor, and it will be sitting on the ground at (50, 300). The second building will have 18 floors and 6 office units per floor, and it will be sitting on the ground at (200, 300).

Just like with Challenge 2, both buildings should be gray (color #999999) and each office should be 16 x 16 width 4 pixels of padding around the whole building.

Quick Reference:

Previous Challenge: View your code from Stage 1 Challenge 2 to use on this challenge.

Code Missing: You have not yet entered any code in to the previous challenge: Stage 1 Challenge 2
Stage 1 Challenge 2
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## Use translate() to Position the Building

Now we are going to clean up our functions a little bit.

A well-written function is like a polite robot who comes over to your house to do a job, and then leaves everything exactly as it found it. But if you look at the function used to draw a French flag in the previous example, it wasn't so tidy. It changed the context.fillStyle to '#EF4135' and never changed it back.

To make our function more tidy, we are going to call context.save() at the start of the function and context.restore() at the end of the function. Calling context.save() saves the state of the context (including the current context.fillStyle), and context.restore() restores the context to the last time you saved it.

The other change we are going to make to our function is to use context.translate(). Notice how we had to do some calculations with x and y to figure out the positions of the white and red rectangles in the French flag? Imagine you had to do the same calculations for a hundred windows in a building. By using context.translate(), we can eliminate a lot of that math.

Calling context.translate() moves the origin of the context. If we move the origin of the context to the top left corner of the flag, then we can draw the rectangles in the flag as though the flag is positioned at (0, 0). The math is much easier. However, when using context.translate(), it's even more important to save and then restore the context. If you think changing the context.fillStyle is rude, changing the origin of the context and not changing it back is much ruder!

(As an exercise, try to predict what would happen if you took out the context.save() and context.restore() from the function. You'll have to reset the example and then refresh the entire page to get everything back to normal.)

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## Challenge 4

Tidy up the drawBuilding() function from Challenge 3 in the same way. Call context.save() at the start of the function and context.restore() at the end of the function, and use context.translate() to move the origin to (x, y).

Once the drawBuilding() function is tidy, draw one building with 12 office units per floor and 6 floors sitting on the ground at (40, 300) and another building with 10 office units per floor and 15 floors at (280, 300).

Just like with Challenges 2 & 3, both buildings should be gray (color #999999) and each office should be 16 x 16 width 4 pixels of padding around the whole building.

Quick Reference:

Previous Challenge: View your code from Stage 1 Challenge 3 to use on this challenge.

Code Missing: You have not yet entered any code in to the previous challenge: Stage 1 Challenge 3
Stage 1 Challenge 3
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