The haftarah of Shabbos Chazon begins with the words חזון ישעיה, "Yeshayahu's vision," and therefore, the Shabbos is called Shabbos Chazon. The haftarah discusses the churban, and we wonder, why do we name this Shabbos after sad events? As the Kedushas asks, "Why is this Shabbos called Chazon? It isn't praise for Yisrael!"
The Kedushas Levi answers (Drushei Tzemech Tzaddik, Eichah) that on this Shabbos, Hashem shows every Yid how the world will be when the third Beis HaMikdash is built. Shabbos Chazon means the Shabbos of visualization because we can see the future world. The Kedushas Levi explains it with a mashal:
A king gave his son an expensive set of clothing, but the prince wasn't careful, and he ripped and soiled the clothing. The king ordered another set of clothes, but the prince also ruined those. The king ordered a third set of royal clothes, showed it to his son, and said, "When I see you can take care of your clothing, I will give it to you." Once a year, the king would take out the beautiful clothes and show them to his son. He would tell his son, "When you are responsible and ready, I will give you the clothes." This is what occurs each year on Shabbos Chazon. Hashem shows us the third Beis HaMikdash and what life will be like at that time, and then Hashem tells us, "When I see you are ready, I will give it to you."
The Tzaddikim of Bobov zt'l say that it is advised to accept Shabbos early on Shabbos Chazon so that we can turn some of the mourning into a time of joy. The Ohev Yisrael writes," There is reason to say that Shabbos Chazon is the greatest Shabbos of the year." We would think that Shabbos Chazon is the lowest Shabbos of the year as it is in the Nine Days and moments before the destruction of the holy Beis HaMikdash. Furthermore, according to halachah, there are aspects of mourning on Shabbos Chazon. How can this Shabbos be the greatest Shabbos of the year?
The Gemara (Yevamos 62:) says that the love between people increases before separation. The Ohev Yisrael explains that at the time of the Destruction, the love between Hashem and the Jewish nation was at its peak, as it was a moment before a separation. This is the specialness of this Shabbos, greater than all Shabbosim of the year. It is a time of closeness with Hashem. The Midrash says, "There wasn't a holiday for Yisrael like the day the Beis HaMikdash was destroyed." How can Tisha b'Av be called a holiday? The Ohev Yisrael answers that it is because of closeness with Hashem that we experienced during this bitter time of separation.
Rebbe Bunim of Peshischa zt'l said: Some people think being happy on Shabbos is a madreigah for tzaddikim and not applicable to the average person. Because what connection does a regular person have with Shabbos? But they are mistaken. If someone is mechallel Shabbos, he is חייב מיתה. So, just as an average person is associated with the severity of desecrating the Shabbos, he is also associated with the joy of Shabbos.
